Cooling System For A Data Server Center


INTRODUCTION

Background
Stock exchange is a major business sector dependant on share prices. The share prices need to be up to date all the time, for a tradesman to be profitable this industry. Due to the time delay between the London stock exchange and the Johannesburg stock exchange, there is a need to build a new live data center in South Africa to avoid share prices not being current.

Scope of Work

Problem Statement
Data centers contain specialized equipment that need cooling. The equipment within these data centers have very specific cooling requirements that need to be accommodated. These centers must be available 100% of the time all year around, as any down time could result in major losses on the Stock Market. Due to the minimum space available in city hubs, the maximum number of sever racks needs to be installed within the data center space.

Objective
Determine the maximum number of racks that the data center can contain. A people kitchenette also has to be accommodated for in the same space.

Design an efficient Cooling System for the data server center. A new detailed design is required for a heat exchanger. However the rest of the components of the system must be sized and can be bought off the shelf.
Objective breakdown

A complete design describing the entire cooling system for the data center.
Detailed design is required for the heat exchanger
Provide assembly and component drawings
Include any structural components such a support bases, pipe supports etc.
Remaining components of the system must be sized
Components can be bought off the shelf

User Requirements
The data server center will be in a basement of an existing building.
Clients will be able to rent space from the JSE for their own server/s.
The cooling system needs to be available 24hrs a day all year around.
The data server center must accommodate the maximum number of racks within its footprint
The chosen rack brand is APC.
12 servers can be placed on top of one another in a rack
Each server has a load that can vary between 80 ' 300 Watts
The ambient temperature of the data center is to remain between 20-22??C (Setpoint)
The footprint of the data center is 500m^2
The data center will be manned by 4 people
The data center has a kitchenette
HVAC conditions needs to accommodate a people kitchenette

Report Layout

The design report is structured in a build-up fashion, firstly introducing the baseline concepts and then building on the knowledge to complete a cooling system design. The literature survey initiates the report by defining the required knowledge to understand the concepts used in the design. The report then follows to introduce concepts to solve the problem at hand. A final concept is then selected to be designed in detail. Calculations and drawings are produced in order to be able to construct the design. Finally environmental, social and legal aspects are discussed to close off the design.
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LITERATURE STUDY

Introduction
The literature study will be centred on air-conditioning systems. It will outline the basic laws that govern air-conditioning design, i.e. basic laws of thermodynamics, and build the required equations that are needed for analysis.

The study will start by considering the small individual sub-systems and work towards the larger system. It will focus on heat exchangers, however the remaining complementary components will not be neglected.

Law of Thermodynamics
The first law of thermodynamics starts that during any cycle a system (control mass) undergoes, the cyclic integral of the heat is proportional to the cyclic integral of the work (SONNTAG, 2009).

'''??Q= ''??W' (1)

The law simply states that energy is conserved, it can neither be created nor destroyed. Energy can simply just change form from one type of energy to another.

The first law of thermodynamics for a change in state of a control mass can be written as follow.

dE= d(U)+d(KE)+d(PE)=??Q- ??W (2)

E (Total Energy) comprises of Internal energy, kinetic energy and potential energy. Furthermore substituting the equations for all the energy types, the first law can be written as follow. This equation assumes g is constant.

U_2- U_1+ m(v_2^2- v_1^2 )/2+mg(Z_2- Z_1 )=1Q_2-1W_2 (3)

In terms of mass flow rates the equation can be written as follows.

'm ??(u'_2- u_1)+ (m ??(v_2^2- v_1^2 ))/2+m ??g(Z_2- Z_1 )=1Q ??_2-1W ??_2 (4)

Where u is the specific internal energy of the system. For a steady state process the equation becomes.

Q ??+''m ??_i (h_i+ (v_i^2)/2+gZ_i )=''m ??_e (h_e+ (v_e^2)/2+gZ_e )+ W ?? (5)

The application of the first law of thermodynamics for a heat exchanger simplifies to the following. The assumptions are that kinetic energy as well as the potential energy changes are negligible. The work done is zero and that no heat transfer occurs across the control surface.

''m ??_i (h_i )=''m ??_e (h_e ) (6)

The heat transfer for a control volume, in this case the steady state energy equation reduces to. The subscript 'r' refers to the refrigerant side and the 'w' refers to the water side of the heat exchanger.

Q ??=m ??_r '( h_e- h_i) '_r (7)

Q ??=m ??_r '( h_e- h_i) '_r (8)

Coefficient of Performance (COP)
The efficiency of a refrigerator, or in this case of an HVAC system, is measured by the coefficient of performance. The COP (??) is defined as the ratio of the energy that is sought over the energy that it costs for the sought after energy (SONNTAG, 2009). The following case is for cooling.

The typical value of a COP is equals to 2.5 for a household refrigerator (SONNTAG, 2009). This means that 2.5 times more sought after energy is gained when compared to the energy that it costs.

??= (Q_L (energy sought))/(W(energy that costs))= Q_L/(Q_H- Q_L ) (9)

The following coefficient of performance is for heating.

??^'= (Q_H (energy sought))/(W(energy that costs))= Q_H/(Q_H- Q_L ) (9)

The two measures of performance are also interlinked by the following equation.

??^'- ??=1 (9)
Heat Exchangers
Heat exchangers are static equipment, design for efficient heat transfer between two fluids that are at different temperatures. Heat exchanges are not design for mixing of the fluids, hence the fluids are kept separated by a solid wall while the heat transfer process is underway.

Common heat exchangers consist of two loops, a primary and secondary loop. The primary loop containing the fluid with the heat to be transferred and the secondary loop the fluid to extract the heat. Heat exchangers are commonly used in Heating Ventilation and Air-Conditioning (HVAC) applications.

Some heat exchanges exhibits two flow arrangements namely; parallel flow and counter flow arrangements. In the parallel flow arrangement the hot and cold fluid enter the heat exchanger at the same end and flow of the fluid is in the same direction. In the counter flow arrangement the hot and cold water enter the heat exchanger at opposite ends and the flow of fluid is in opposite direction. Each flow arrangement having different effects on the temperature of the exiting fluid.


Figure 2 1: Concurrent and Counter current flow Heat exchangers (Ghajar, 2007)

Types of Heat Exchangers
Heat exchangers come in many shapes and sizes depending on the application. Some Heat exchangers may include:

Shell and Tube Heat Exchangers
Double Pipe Heat Exchanger
Compact Heat Exchanger
Plate Heat Exchanger
Perhaps the most common type of heat exchanger in industrial applications is the shell and tube heat exchanger (Ghajar, 2007).
Shell and Tube Heat Exchangers
Shell and Tube Heat exchangers consist of a large number of tubes packed in a shell with their axes parallel to that to that of the shell (Ghajar, 2007). The heat exchange takes place across the one fluid flowing through the tubes and the other over the tubes, inside the shell. As depicted in the figure below, baffles are in the tube section of the heat exchanger. The function of the baffles are firstly to hold the tubes in place, but more importantly to force the fluid flowing around the tube in a circular motion. This circular motion increases the heat exchange between the two fluids.


Figure 2 2: Shell and Tube Heat Exchanger (Ghajar, 2007)

Double Pipe Heat Exchanger
The double pipe Heat Exchanger is perhaps the most simplest of heat exchangers. It consists of two pipe, one having fluid flowing in the smaller pipe and the other fluid flowing in the annular space between the two pipes.


Figure 2 3: Double Pipe Heat Exchanger (Ghajar, 2007)

Compact Heat Exchangers
Compact heat exchangers are specially designed for a large heat transfer surface area per unit volume. Compact heat exchangers exhibit a very large area density ??. The area density ?? is defined as the ratio of the heat transfer surface area to its volume. Heat exchangers having an area density value of more than 700m^2/m^3 is regarded as a compact heat exchanger.


Figure 2 4: Compact Heat Exchanger (Ghajar, 2007)

Plate Heat Exchanger
A plate heat exchanger, also commonly known as plate and frame heat exchangers, consist of a series of plates with corrugated flat flow passages (Ghajar, 2007). The plate heat exchangers arranges the fluid flow in alternate flow passages. This results in each cold steam being surrounded by a two hot flow steams, resulting in very effective heat transfer.


Figure 2 5: Plate Heat Exchanger (People, n.d.)

Heat Exchanger Advantages and Disadvantages

Type of Heat Exchanger Advantages Disadvantages
Shell and Tube Heat Exchanger Widely known and understood, most common type
Most Versatile in terms of service
Widest range of allowable design pressure and temperatures
Rugged mechanical construction ' can withstand more abuse
Condensation or boiling heat transfer can be accommodated
Thermal stresses can be accommodated inexpensively
Cleaning and repair is relatively straightforward
Low pressure loss Less thermally efficient
Subject to flow induced vibration that can lead to equipment failure
Not well suited for temperature cross conditions
Contains stagnant zones that can lead to corrosion problems
Subject to flow mal-distribution
Double Pipe Heat Exchanger Simple design
Can operate in true counterflow pattern (most efficient flow pattern) Relatively low flow rates
Compact Heat Exchanger Low initial purchase cost
Many different configurations are available
High Heat transfer coefficients
Tend to exhibit low fouling characteristics, due to turbulent flow
Allow significant temperature crosses to be achieved
Require small footprint Narrower range of allowable pressures
Subject to plugging/fouling due to very narrow flow path
Gasketed units require specialised opening and closing procedures
Material of construction is critical since wall thickness is very thin.
Plate Heat Exchanger Require small footprint
High heat Transfer efficiency
Easy to clean
Ideal for transferring heat between two fluids with similar temperatures and flow rates
High corrosion resistance Requires gaskets
Subject to plugging/fouling due to very narrow flow path
Potential for leaks
High pressure loss
Table 1: Types of Heat Exchanger Advantages and Disadvantages (solutions, n.d.)

Fouling Factor
Fouling, otherwise known as sediment buildup, occurs in heat exchangers. Fouling directly affects the heat transfer efficiency of the heat exchanger by reducing heat transfer, impairing fluid flow and increasing the pressure drop across the heat exchanger. Different types of fouling occurs, depending on the type of fluid and operation conditions. Due to the nature of the equipment, fouling could cause increase in electrical expenses and impair a working system. Common practice is to account for fouling in design stage, by increasing the effective surface area of the heat exchanger, but this incurs extra startup cost for the client.


Figure 2 6: Fouling (Online, n.d.)
Life Expectancy (Heat Exchangers with water in the tubes)
The life expectancy of a heat exchanger depends on multiple factors. The following section just outlines some factors affecting the life expectancy of heat exchangers according to the company: Delta T Heat Exchangers (Exchangers, n.d.).

Factors affecting the fife expectancy of heat exchangers:
Maintenance (Frequency and Scope)
Water Supply
Chemistry
Temperature
Operating Factors

Common Causes of heat exchanger replacements:
Fouling
Tube Leaks
Tube joint leaks
Channel / Headers
Corrosion
Freezing

Chiller
Chillers consist of four components. These four component work together to accept heat at one location and reject the heat at another location.

Chiller consist out of the following:
Compressor
The aim of the compressor is to increase the pressure and temperature of a fluid.
Condenser
A condenser is a device used to condense a gas or a vapour into a liquid. In the HVAC industry a condenser is used to condense the refrigerant to a liquid, and in doing so it rejects its contained heat.
Expansion Valve
The aim of the expansion valve is to decrease the pressure and temperature of a fluid.
Evaporators
An evaporator is a device used to evaporate a liquid into a gas or a vapour. In the HVAC industry an evaporator is used to evaporate the refrigerant to a gas or vapour, and in doing so it accepts heat.

Vapour-Compression Chillers
Vapour-compression chillers operate on the principles of the vapour-compression cycle, or more commonly known as the refrigeration cycle. The cycle uses a working fluid to change phase repeatedly, absorbing heat in one phase and rejecting heat in another.
Vapour-Compression Cycle
The figure blow depicts a schematic view the ideal vapour-compression cycle (1-2-3-4-1). The figure on the left depicts the components in use, while the figure on the right depicts a temperature vs. entropy graph.

Starting at state 1 on the figure. The saturated vapour at low pressure enters the compressor and undergoes compression. Here the temperature and the pressure is increased. The fluid now is a superheated vapour.

The fluid then enters the condenser at state 2, here the fluid changes phase from a vapour to a liquid while moving through the condenser. The fluid then subsequently rejects heat at a constant pressure. This is represented by Q_H in the figure below.

At state 3 the fluid is a saturated liquid. The fluid then moves through the expansion valve, between state 3 and 4, to decrease the pressure of the fluid before it enters the evaporator. The fluid now is a liquid vapour mixture.
The fluid then enters the evaporator and absorbs heat, changing phase from a liquid to a vapour, before completing the cycle and entering the compressor again. This process is represented by Q_L in the figure below. The process now repeats itself.


Figure 2 7: Ideal vapor-compression cycle (SONNTAG, 2009)
The process indicated by the process 1'-2'-3'-4'-1' is the ideal Carnot cycle representing the cycle with maximum efficiency.


Figure 2 8: Vapor-Compression Chiller (Faculty, n.d.)

Vapour-compression chillers are further classified according to the type of compressor that it uses. Three basis types of compressors are available.

Compressor
The aim of the compressor is to increase the pressure and temperature of the refrigerant in order for it to reject its heat at the condenser. The compressor uses work, shaft work created by electrical power, to increase the pressure. Referring to Figure 3-2: Ideal vapour compression cycle, the compressor operates between states 1 and 2.

Three common types of compressors are as follow:
Reciprocating
A reciprocating compressor is a positive displacement machine, meaning the increase the pressure of a fluid by reducing its volume (Toolbox, n.d.). This compressor takes volumes of fluid which is confined, and increases it pressure. The compressor accomplishes this by means of a piston within a cylinder, creating the pressure increase.
Rotary Centrifugal
Centrifugal compressors are dynamic compressors which depend on transfer of energy from a rotating impeller (Toolbox, n.d.). Centrifugal compressors produce high-pressure discharge by converting angular momentum imparted by the rotating impeller.

Centrifugal compressor's impeller rotates at a very high speed to accomplish the compression efficiently. Centrifugal compressors are design for high capacity since there is a continuous flow of fluid trough the compressor.

The impeller is driven by an AC motor that is controlled by a variable frequency drive (VFD). The VFD controls the speed of the motor by varying the frequency of the motor. The speed of the motor is directly proportional to the amount of force exerted on the refrigerant. Therefor the greater the speed of the motor the greater the exiting pressure of the refrigerant, that also intern causes an increase in the efficiency of the chiller.

Varying the speed of the motor compensates for the varying demands of the system.
Rotary Screw
Rotary screw compressors is a positive displacement compressors (Toolbox, n.d.). Screw type compressors consist of two rotors within a casing where the rotors compress the fluid internally.

Compressor Advantages and Disadvantages

Type of Compressor Advantages Disadvantages
Reciprocating Compressor Simple design
Easy to install
Lower initial cost
Large range of power
Two stage models offer highest efficiency Higher maintenance cost
Many moving parts
Potential for vibration problems
Many are not designed to operate at full capacity
Rotary Centrifugal Compressor High efficiency
Can reach high pressures High initial cost
Complicated monitoring and control
High rotational speed require special bearings
Specialized maintenance considerations.
Rotary Screw Compressor Simple design
Low to medium initial and maintenance cost
Two-stages design provide good efficiency
Easy to install
Few moving parts High rotational speed
Shorter life expectancy than other compressors
Single stage design have lower efficiency
Difficult with dirty environment
Table 2: Types of Compressor Advantages and Disadvantages (Technology, n.d.)

Suction Accumulator
The suction accumulator is a secondary component to prevent damage occurring to the compressor. It allows only for vapour to enter the compressor.


Figure 2 9: Suction Accumulator (Business, 2008)

Condensers
Condensers are heat exchangers that allow heat rejection to take place. In the condenser the working fluid is condensed, and hence the name. Since the condenser is essentially a heat exchanger, the type of condenser will depend on the application.

HVAC chilled water systems make use of a condensers to exchange heat from the secondary chilled water loop to the surroundings. The condensers can come in three forms namely; Water cooled condensers, air cooled condensers and evaporative condensers.

Water Cooled Condensers
Water cooled condensing units are heat exchangers that rejects heat into a water source. These condensing units would be used where air-cooled condensing units are undesirable and where space is limited.

Air-Cooled Condensers
Air-cooled condensing units are heat exchangers that reject the heat into the air in the atmosphere. Air-cooled condensers make use of ambient airflow to absorb the heat from the fluid that requires heat extraction. The greatest advantage of this condenser is that no water is needed.

Evaporative Condensers
Evaporative condensing units are heat exchangers that reject heat into water. Evaporative condensers makes use of small water particles evaporating, to remove the heat from the desired fluid into the atmosphere.

A common form of an evaporative heat exchanger is a cooling tower used in the HVAC industry. These type of condensers have an advantage where they provide energy saving by providing lower condensing temperatures than conventional air-cooled and water 'cooled condensing temperatures (Company, n.d.).

Condensers

Type of Condenser Advantages Disadvantages
Water Cooled Condenser Rejects heat to water
Pricey to install
More efficient Rejects heat to water (Could be advantages depending on application)
Regular Service and maintenance
Require water treatment (depending on application)
Air-Cooled Condenser Reject heat to the outdoors
If installed outside of the unit, easiest arrangement
Easy to clean Loose efficiency in dirty environments
High initial cost
Evaporative Condenser Rejects heat to water
Operate at low condensing temperature
Used in large commercial HVAC applications
effective Rejects heat to water (Could be advantages depending on application)
Least popular choice
Not most efficient
Table 3: Types of Condensers Advantages and Disadvantages (Blog, 2013)

Expansion valve
The expansion valve acts as a throttling device to decrease the pressure of the refrigerant. The expansion valve causes a restriction in the flow passage, and intern decreases the pressure of the fluid. A steady state throttling process is approximately a pressure drop at constant enthalpy.

Evaporators
Evaporators are heat exchangers that allow heat absorption to take place. In the evaporator the working fluid is evaporated, and hence the name. Since the evaporator is essentially a heat exchanger, the type of evaporator will depend on the application.

In the case of shell and tube type evaporators (heat exchangers), the fluid to be chilled flows along the shell side and the refrigerant flows along the tube side of the heat exchanger.

In HVAC applications the Air-Handling units is regarded as an evaporators.

Air-Handling Units
An air-handling unit is a piece of equipment used in the HVAC industry to circulate cooled air in a space that requires air-conditioning. AHU is a static piece of equipment, equipped with a fan and a looped coil where the cold refrigerant flows through. The AHU has an air inlet side where the fan pulls air in form and forces the air over the cold coils. The heat from the air is the rejected to the cold refrigerant inside the coil and this interns reduces the temperature of the air. The air is the forced into the required air-conditioning space, and interns cools the space.

Chilled Water Systems
Chilled water systems work on a principle just as the name implies. The systems exploits the basic law of thermodynamics that energy/heat always travels from hot to cold. Using this principle the system incorporates chilled water into the air-conditioning system to absorb heat from the desired location, and reject the heat elsewhere.

Chilled water systems consist of 3 critical components namely a chiller, condenser (i.e. Cooling Tower) and an evaporator (i.e. Air-Handling Unit). These three components form the center of the cooling system and these independent components cannot accomplish the air-conditioning task independently, but must to work together as one system.

Each component has a specific task at hand. The chiller forming the central 'heat exchanger' between the condenser and the evaporator. The system consists of three fluid flows, in and around the chiller. Two fluid flows form the two chilled water loops namely the primary (Supply and Return) and secondary chilled water loop (Condenser Water Loop). The third fluid flow is the refrigerant fluid flow inside the chiller, never coming into with the other two chilled water loops.


Figure 2 10: Chilled Water System (Faculty, n.d.)
The refrigerant fluid flow forms the heart of the cooling system, where it's responsible for the main heat absorption and heat rejection of the system. As the refrigerant flow moves through the chiller, i.e. evaporator, expansion valve, condenser and compressor, as it completes the vapor compression cycle (Green loop, in Figure 2-1).

The chilled water system exploits the vapor-compression cycle by incorporating another two loops. This is where the primary and secondary chilled water loop comes into working.

The primary chilled water loop connects the chiller and the air-handling unit (AHU). The AHU, typically situated inside the area that requires cooling, receives the chilled water. The AHU consists of a fan arrangement inside its enclosure, this fan now blows warm air over the chilled water loop. This intern removes the heat from the air, and the cooled air is then supplied to the area that required cooling. The chilled water, now containing the absorbed heat from the air, now loops back to the chiller. At the chiller the heat contained in the water, now gets rejected in the evaporator to the refrigerant fluid. The primary loop cycle then repeats itself.

The secondary chilled water loop connects the chiller to the condenser (i.e. Cooling Tower). The secondary chilled water loop now absorbs the heat from the condenser, inside the chiller, and transports it to the cooling tower. The cooling tower now acts as a heat exchanger and rejects the heat into the atmosphere. The secondary loop cycle then repeats itself.

Thermal Storage Systems
Thermal storage system have been in operation for many years, however mainly catering for the dairy industry. Recently thermal storage units have been incorporated into the comfort cooling industry due to the large energy demand on the cooling system in a building.

Thermal storage systems are classified into two categories. Full or partial thermal storage.

Full Thermal Storage Systems
Full thermal storage systems exploit low off peaks electrical rates during the night time to operate a chiller. The chillers generates ice (Thermal Storage) during the night, and use the ice during the day, when peak electrical tariffs are active, to provide cooling to the building.

The full thermal storage system has two modes of operation, ice build and ice melt out.
Ice Build
During the ice build stage, which occurs during the off-peak times at night, the glycol chillers are in full operation. The chillers now generate low temperature glycol that circulate through the tubes in the thermal storage unit. The glycol removes the heat in stored in the water and hence causes the water to freeze and form ice around the tubes where the glycol flows through.

Ice Melt Out
During the ice melt out, which occurs during the peak times in the day, the glycol chillers are completely off. Depending on the melt out type, either glycol is circulated through the tubes or water is circulated over the tubes to extract the stored energy in the ice. The glycol or water is now circulated through the primary side of the heat exchanger. Simultaneously the chilled water from the building circulates through the secondary side of the heat exchanger where it is cooled by the ice water from the thermal storage system. The chilled water is the circulated to the building where it is used to cool the building.


Figure 2 11: Thermal Storage System Schematic (Evapco, n.d.)

Partial Thermal Storage Systems
Partial thermal storage incorporates a reduced size chiller that operates in conjunction with the thermal storage unit to meet the peak load demand of the building. Partial thermal storage systems are used to 'shave off' peak time load demands my flattening the load of the building.

Melt Out Types
Two types of met out operations exist namely internal and external melts.
Internal Melt
The internal melt types melts the ice from the inside out as the name suggests. The glycol circulates through the thermal storage coils and melts the ice build-up. The tank water never leaves the tank in an internal melt system.

Internal melt has a specific performance incorporated, this can be seen in figure 2-11. Early in the cycle the glycol temperature rises and drops off later in the cycle. As a result the internal melt system is great for load that peak at the end of the melt out cycle.

Figure 2 12: Internal Melt Profile (Evapco, n.d.)
External Melt
The external melt types melts the ice from the outside in as the name suggests. The warm water that returns from the heat exchanger melts the ice build-up.

External melt has a specific performance incorporated, this can be seen in figure 2-12. Early in the cycle the glycol temperature is very stable and rises later in the cycle. As a result the external melt system is great for load that peak at the beginning of the melt out cycle.

Figure 2 13: External melt Profile (Evapco, n.d.)
Air Agitator System
The air agitator system is a vital part of the thermal storage system. The agitator is necessary for the optimal operation of the thermal storage system. The agitator is necessary to agitate the tank water during the initial build-up and cool down periods

Refrigerant
A refrigerant is a fluid used in a heat cycle, such as the refrigeration cycle, to undergo phase change to accommodate the acceptance or rejection of heat.

Some refrigerants, mainly chlorofluorocarbons (CHCs) have been banned from use due to their destructive nature on the ozone. Refrigerants need to be carefully selected to have a low toxicity, low flammability and long atmospheric life.

CFCs have been phased out of use according to the 1987 Montreal Protocol. CFCs have been replaced by halogenated chlorofluorocarbons (HCFCs), however these refrigerant are also due for phase out during the 21st century. Common refrigerants used in chiller according to the National Refrigerant Reference Guide (Guide, 2011 ) are:

Refrigerant Name Components Type Temp Glide (') Lubricants Comments
R-22 Pure HCFC 0 Mineral oil or Alkylbenzene Chiller
R-123 Pure HCFC 0 Mineral oil or Alkylbenzene Low Pressure centrifugal chillers
R-134a Pure HFC 0 Polyolester Centrifugal Chiller
Table 4: Refrigerant Types (Guide, 2011 )
According to the Montreal Protocol:
R-134a has no restrictions and no phase out date
R-123 will be phased out in 2030
R-22 will be phased out in 2020

Air-Conditioning National Standards
SAIRAC (South African Institute of Refrigeration and Air-Conditioning) are the national regulators in terms of air-conditioning regulations. SAIRAC follow the standards produced by the South African Bureau of Standards (SABS). SAIRAC provides a short list of standards applicable to refrigeration and Air-Conditioning, but confirm this list is by no means comprehensive (Anon., n.d.).

In South Africa the Standards produces by American Society of Heating Refrigeration and Air-Conditioning Engineers (ASHRAE) (Anon., n.d.) are also accepted.

Cooling Requirements for Server Centres
Data server centres contains equipment with very specific cooling requirements. Designers of these equipment strive to ensure the equipment are as efficient as possible and the cooling conditions should strive to compliment the efficiency of the equipment installed.

Standards
ASHRAE (American Society of Heating Refrigeration and Air-Conditioning Engineers) have published guidelines for data centre environments under ASHRAE TC 9.9.

ASHRAE TC 9.9
2011 Thermal Guidelines for Data Processing Environments ' Expanded Data Centres / Classes and Usage Guidelines (Engineers, 2011).

According to TC 9.9 - Pg. 7
Class A1: Typically a data center with tightly controlled environmental parameters (dew point, temperature and relative humidity) and mission critical operations; types of products typically designed for this environment are enterprise servers and storage products.

The user requirement point 5 (The ambient temperature of the data center is to remain between 20-22??C) falls within the requirements set out by the standard.


Table 5: 2011 ASRAE Thermal Guidelines (Engineers, 2011)

Ventilation Requirements for Server Centres
The data centre is occupied by 4 people and therefor require a minimum amount of fresh air set out by ASRAE. The data center also incorporates a kitchenette and therefor requires a minimum amount of exhaust air to be extracted according to ASRAE.

Fresh Air Standards
According to ASRAE Standard 62-2001 (Ventilation for acceptable indoor air-quality). The minimum ventilation rates in a 'Breathing Zone' for a computer lab is as follow.

People outdoor air rate:
5L/s per person

Area outdoor air rate:
0.6 L/s per m^2

Exhaust Air Standards
According to ASRAE Standard 62-2001 (Ventilation for acceptable indoor air-quality). The minimum exhaust air rate is as follow:

Kitchenette exhaust air rate:
1.5L/s per m^2

Air Circulation Requirements (Duct Work Regulation)
The South African National Standards (SANS) govern the Air Circulation requirements.

The relevant codes are as follow:
SANS 1238 ' 2005: Air-Conditioning Ductwork
SANS 10173 ' 2003: The installation, testing and balancing of Air-Conditioning Ductwork

Piping Circulation Requirements
The South African National Standards (SANS) govern the Piping Circulation requirements.

The relevant codes are as follow:
SANS 10140-3 ' 2003: Identification colour marking Part 3: Contents of Pipelines
SANS 1445-3 ' 2008: Thermal Insulation materials for industrial applications Part3: Bonded preformed material fibre pipe sections

Heat Exchanger National Standards
In South Africa vessels under pressure are governed by section 43 of the Occupational Health and Safety Act, 1993 (Act 85, 1993) - Vessels under Pressure regulations, 1996.

ASME (American Society of Mechanical Engineers) and TEMA (Tubular Exchangers Manufacturing Association) also have produced standard pertaining to pressure vessels/heat exchangers. ASME is internationally recognised and accepted by most mechanical engineers.

The design in the report will focus on using ASME standards. Specifically ASME (BPVC) Boiler and Pressure Vessel Code ' Section 8 (Pressure vessels).

Conclusion
The literature study outlined all critical literature in order to understand and analyse the problem. The gained knowledge from the literature study will now be used to formulate a functional analysis of the problem statement, and breakdown the problem in order to solve the problem step by step.

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FUNCTIONAL ANALYSIS

Introduction
The functional analysis will focus on the cooling system. This chapter will decompose the system into smaller components and describe the function of each component.

Functional Components
The main functional components of a cooling system is as evaporator, condenser and a heat exchanger.

A Cooling System comprises of three main components:
Evaporator
Condenser
Heat Exchanger


Figure 3 1: Cooling System Decomposition
A cooling system comprises of all these components, and cannot function with even one component missing. Figure 3-1: Cooling System Decomposition, visually depicts the function of each component.

Depending on the specifics of the system required the system can incorporate more components. Figure 3-1 depicts the basic decomposition of a cooling system.

Evaporator
The evaporator is essentially a heat exchanger. The aim of the Evaporator is to accept heat inside the area that is to be cooled. Typically in large industrial applications the evaporator comes in the form of an AHU (Air Handling Unit). An AHU makes use of chilled water to accept the heat from the warm air that is blown over the AHU coils. The warm are in intern cooled and supplied to the area that requires cooling.

Heat Exchanger
A central heat exchanger is typically incorporated into the system to exchange heat between the evaporator and the condenser. The aim of the heat exchanger is to exchange the heat between the two components.

Heat Exchangers typically comes in one of the forms mentioned in section 2.4.

Condenser
The condenser is essentially a heat exchanger. The aim of the condenser is to reject the heat, accepted from the heat exchanger, to another medium. Typically in large industrial applications the condenser comes in one of the forms mentioned in section 2.7.

Conclusion
The functional analysis of the cooling system, and each of its components, has been discussed and decomposed for a better understanding. Each component forms a vital part in the cooling system and the components need to work together to accomplish the common goal.

'
DESIGN REQUIREMENTS AND TECHNICAL SPECIFICATIONS

Introduction
Design requirements and technical specifications form the basis of the design. Chapter 4 outlines the importance of different parameter affecting the cooling system design. The relevant specifications are also indicated.

Requirements
A complete design describing the entire cooling system for the data center is required. A detailed design is required for the heat exchanger, whereas the remaining components need to be sized and bought off the shelf.

The following table describes the importance level of design requirements.

Requirement Not Very Important Relatively Important Very Important
Heat Removal Capability
Reliability
System Efficiency
Environmental, Social and Legal concerns (Safety)
Noise
Refrigerant
Size
Cost
Manufacturability
Maintenance
Mass
Table 6: Design Requirements Importance Level

Requirement Breakdown
Heat Removal Capability
The system first and foremost needs to remove heat from the required area. This is the main requirement for the system.
Reliability
The data centre needs to be available 24hrs a day all year around. No compromise can be made when considering reliability. The reliability is top priority for the design. The rating for reliability is there for very important.
System Efficiency
The data centre needs to be available 24hrs a day all year around. Efficiency cannot be compromised as power consumption needs to be kept at a minimum. The greater the efficiency the lower the operation costs will be. The rating for efficiency is there for very important.
Environmental, Social and Legal concerns (Safety)
The data centre is located in the city hub of Johannesburg so the environment is filled with people and natural life. The system needs to be environmentally friendly, not harming the environment. The chiller needs to be safe to operate and maintain.

The system must not disturb the social aspects of the city life and the working environment around it. The system must also comply with all legal matters pertaining to the design.
Noise
The data centre is located in the city hub of Johannesburg, where many businesses are located. The noise level will need to be kept at a minimum to accommodate for the employees of the surrounding businesses. The rating for noise is there for very important.
Refrigerant
The refrigerant used is connected to the efficiency and the environmental impacts of the system. Refrigerant selection is very important for sustainability of the world. The rating for refrigerant is there for very important.
Size
The data centre is located in the city hub of Johannesburg. Space is very restricted, however the assumption is that there are no space restriction. The rating for size is there for relatively important.
Cost
The running cost is interconnected with the maintenance of the project. The better the reliability of the system and the better the maintenance the less the running cost will be. There is no cost restriction on running cost however running cost has to be considered. The rating for running cost is there for relatively important.
Manufacturability
Manufacturability is an important aspect to all mechanical engineers. The system needs to be manufactureable in order for the system to perform its duty. The rating for manufacturability is there for relatively important.
Maintenance
The data centre is located in the city hub of Johannesburg where many artisans and maintenance personnel are located. Maintenance is very important and should be conducted on a regular basis. The rating for initial cost is there for relatively important.
Mass
The system will be located on the ground level next to the building. The support structure will be on the outside floor not affecting any building below, as in the case of placing the chiller on the roof. The rating for mass is there for not very important and does not fall under the scope of the project.

Specifications
The following is a table representing the specifications for the cooling system.

Cooling System Specifications
Spec No. Need
1 Ambient temperature inside the data center needs to remain between 20-22 ' (Set Point)
2 Cooling System needs to be available 24hrs a day
3 Air-condition inside the server room needs to be suitable for people
4 Air-condition inside the server room needs to be suitable for a kitchenette

Data Center Specifications
Spec No. Need
5 The data server center will be in a basement of an existing building
6 Clients will be able to rent space from the JSE for their own server/s
7 The data server center must accommodate the maximum number of racks within its footprint
8 The chosen rack brand is APC
12 servers can be placed on top of one another in a rack
Each server has a load that can vary between 80 ' 300 Watts
9 The footprint of the data center is 500m^2
10 The data center will be manned by 4 people
11 The data center has a kitchenette

Data Center Variables

Variable No. Variable
1 Server Rack model not specified
2 Kitchenette equipment not specified
3 Activity of personnel not specified

Conclusion
The chapter discussed the different requirements and their importance level. The most important design requirements are:
Heat Removal Capability
Reliability
System Efficiency
Environmental, Social and Legal (Safety) concerns
Noise
Refrigerant

'
SYSTEM CONCEPTS

Introduction
Chapter 5 will focus on system concepts. The chapter will analyse concepts that can solve the problem of the cooling of the data center as a whole. The system concepts will be discussed, analysed and a system solution selected. Chapter 6 will discuss detailed concepts for the heat exchanger design.

Concept 1: Conventional Vapour Compression Chiller System
Concept 1 incorporates a conventional vapour compression chiller. The system comprises of a refrigerant that cycles through the vapour compression cycle. The refrigerant changes phase to accept or heat at the evaporator and reject heat at the condenser. Refer to section 2.5.1 for a detailed explanation on the vapour compression cycle.

Compressor
The system concept will make use of one of the compressors listed.
Reciprocating
Rotary Centrifugal
Rotary Screw

Refer to section 2.6 for a detailed explanation of the different compressors.

Condenser
The system concept will make use of a condenser outside. The condenser will be either one of the condensers listed.

Water Cooled Condenser
Air Cooled Condenser
Evaporative Condenser (Could be a cooling tower as shown in the figure)

Refer to section 2.7 for a detailed explanation of the different Condenser units.

Expansion Valve
A standard off the shelf expansion valve will be used.

Evaporator
A standard air-handling unit will be used as the evaporator inside the data center. The AHU will incorporate a ducted system with louvers.

System Layout
Figure 5-1 depicts a conventional Chiller system used in industry.

Figure 5 1: Convectional Vapor Compression Chiller System (Faculty, n.d.)

Concept 2: Thermal Storage System
Concept 2 incorporates an Ice Bank Thermal Storage Unit. The system will incorporate a Thermal storage unit purchase off the shelf. The heat exchanger will be designed in detail. Refer to section 2.11 for a detailed explanation of the Thermal Storage System

Heat Exchanger
The system concept will make use of a heat exchanger to exchanger the heat collected inside the data center with the cool Ice water from the thermal storage unit. The heat exchanger will be either one of the exchangers listed.

Shell and Tube Heat Exchangers
Double Pipe Heat Exchanger
Compact Heat Exchanger
Plate Heat Exchanger

Refer to section 2.4 for a detailed explanation of the different Heat Exchangers.

Evaporator
A standard air-handling unit will be used as the evaporator inside the data center. The AHU will incorporate a ducted system with louvers.

System layout
Figure 5-2 depicts an Ice Bank Thermal Storage system.

Figure 5 2: Thermal Storage System (Evapco, n.d.)

Thermal Systems in Operation
The thermal storage system have been successfully implemented in data server centres. An article about Intel, confirms that thermal storage at a data server center is both reliable and saves costs (Facilitiesnet, n.d.). A chilled water storage system kept one of Intel's large regional hub data centers cool, when a power outage that lasted several hours caused the chillers to shut down (Facilitiesnet, n.d.). The thermal storage system provided enough cooling to the system and kept the facility in operation while maintenance could resolve the problem.

Google whom have also incorporate thermal storage into their data centres. Google initiated a $300 million data center project in Taiwan, that uses thermal energy storage to keep equipment cool during the day (Arstechnica, n.d.).

To name a few more existing data centers that incorporate thermal storage.
Phoenix ONE data center (Knowledge, 2012)
350 East Cermak (Knowledge, 2012)
National Petascale Computing Facility (Knowledge, 2012)
The National Oceanographic and Atmospheric Administration (Knowledge, 2012)

System Comparison
Type of System Advantages Disadvantages
Conventional Vapour Compression Chiller System More common
High COP
Reliable
Industry known Noisy
Uses Refrigerant
Thermal Storage System Durable
Reliable
Low refrigerant Content
Extra High Cooling Power for Peaks
Very stable ice water temperature below 1'
Safe
Environmentally Sustainable
Indirectly reduces carbon emissions
Reduce operating cost
Incorporated less expensive power at night
Recognised by ASHRAE as a green initiative
Provides operational Flexibility
Complex design
Space consuming
More components than Conventional system
Greater Maintenance
Table 7: Cooling System Advantages and Disadvantages

Selection
The selection will be make based on the flowing criteria. A simple selection technique will be incorporated. A '1' in the table will represent that the system performs better in that specific criteria, when compared to the other system. The '0' in the table will represent that the system performs worse in that specific criteria, when compared to the other system.
Heat Removal Capability
The thermal storage has the capability to create large temperature differences at the heat exchanger, hence increased heat removal capability. The thermal storage system can sustain a large temperature difference for a sustained period of time depending on the size of the system.
Reliability
The thermal storage system is very reliable as it can be sized to be able to accommodate the cooling requirement for a period of time without the chiller being in operation.
System Efficiency
The thermal storage system is very efficient since it uses cheap electrical power during the night to store the cooling capacity for the following day. Hence the cooling capability is cheaper and electrical energy cost to mechanical cooling is more efficient.
Environmental, Social and Legal concerns (Safety)
The thermal storage system incorporates less refrigerant hence having a less of an impact on the ozone. The thermal system is recognised by ASHRAE as a green initiative.
Noise
The thermal energy unit will create less nice since the chiller will be off during the day while people are working and running at night while people are not in the city hub.
Size
The conventional system will require less space to operate in since it comprises of less components.
Cost
The conventional system will have less expenses since it comprises of fewer components.
Manufacturability
The conventional system will be easier to manufacture since it comprises of fewer components.
Maintenance
The conventional system will have simpler maintenance procedures sine it comprises of fewer components.
Mass
The conventional system, typically requires a larger chiller that compared to the thermal storage unit. However the mass of the storage tank also needs to be taken into consideration therefore the conventional system has a smaller weight requirement.

Selection Table

Criteria Weighting Conventional Score Thermal Storage Score
Heat Removal Capability 15% 0 0% 1 15%
Reliability 15% 0 0% 1 15%
System Efficiency 15% 0 0% 1 15%
Safety 10% 0 0% 1 10%
Noise Generation 10% 0 0% 1 10%
Size 7.5% 1 7.5% 0 0%
Cost 7.5% 1 7.5% 0 0%
Manufacturability 7.5% 1 7.5% 0 0%
Maintenance 7.5% 1 7.5% 0 0%
Mass 5% 1 5% 0 0%
TOTAL 100% 35% 65%
Table 8: Selection Table

Conclusion
The system chosen to accommodate the cooling of the data server center is the Thermal storage unit. The selection is based on the selection table in table 7.

The thermal storage system has many advantages over the conventional system. The greatest being that the system is environmentally sustainable.

HEAT EXCHANGER CONCEPTS

Introduction
Chapter 6 will focus on heat exchanger concepts. The chapter will analyse concepts that can solve the problem of the heat exchanger catering for the cooling system of the data center. The heat exchanger concepts will be discussed, analysed and a solution selected.

Selection Criteria and Weighting
The following table outlines the selection criteria and their weighting:

Criteria Weighting
Heat Removal Capability 15%
Reliability 15%
System Efficiency 15%
Safety 10%
Noise Generation 10%
Size 7.5%
Cost 7.5%
Manufacturability 7.5%
Maintenance 7.5%
Mass 5%
TOTAL 100%

Refer to section 4.2.1 for a detailed breakdown of the selection criteria.

Concept Generation
Refer to section 2.4.1 for a brief explanation of different types of heat exchangers. Section 6.2.1 will discuss heat exchanger concepts to solve the heat exchange problem.

*Please note that the following schematics are merely to portray the concept, in no way what so ever is the cold fluid and hot fluid orientation final. Further investigation is needed to determine exact orientation.

Concept 1
Concept 1 is a Shell and Tube Heat Exchanger in a One-Shell Pass and One-Tube Pass configuration. Shell and tube heat exchangers come in many shapes, sizes and configurations. Concept 1 will outline one of these configurations and its benefits. Since Shell and Tube heat exchangers are the most commonly used heat exchanger, 2 concepts will be generated for this type of heat exchanger.


Figure 6 1: Shell and Tube Heat Exchanger (One-Shell Pass and One-Tube Pass)
The shell and tube heat exchanger is perhaps the most common type of heat exchanger. The principle is such that one fluid flows through the shell part of the heat exchanger and the other fluid through the tubes. In the case of figure 6-1 the cold fluid is flowing through the shell and the hot fluid is flowing through the tubes.

The shell incorporates a baffle that forces the tube side fluid to flow in a circular fashion as seen in figure 6-1. The circular flow increases heat transfer between the two fluids before the shell side fluid exits the heat exchanger. The hot fluid enters at the front side of the heat exchanger and exits in the rear. The hot fluid flows through straight tubes across the heat exchanger.

Shell and tube heat exchangers can be very large or very small depending on the size the application requires. The shell and tube is very rugged and can withstand more abuse that most heat exchangers. Shell and Tube heat exchanger also displays the widest range of allowable design pressure and temperatures.

Concept 2
Concept 2 is a Shell and Tube Heat Exchanger in a U-Tube configuration.


Figure 6 2: Shell and Tube Heat Exchanger (U-Tube Type)

Concept 2 is much like concept one except for being in a different configuration. The principle is such that one fluid flows through the shell part of the heat exchanger and the other fluid through the tubes. In the case of figure 6-2 the cold fluid is flowing through the shell and the hot fluid is flowing through the tubes.

The shell incorporates a baffle that forces the tube side fluid to flow in a circular fashion as seen in figure 6-2. The circular flow increases heat transfer between the two fluids before the shell side fluid exits the heat exchanger. The hot fluid enters at the front side of the heat exchanger and exits in the front, due to the U-Tube configuration. The hot fluid flows through the U-Shape tubes across the heat exchanger and back.

Shell and tube heat exchangers can be very large or very small depending on the size the application requires. The shell and tube is very rugged and can withstand more abuse that most heat exchangers. Shell and Tube heat exchanger also displays the widest range of allowable design pressure and temperatures.

Shell and Tube heat exchanger are very common and widely known. Shell and tube heat exchangers are thus widely known and understood.

Shell and Tube heat exchangers are very popular and a must have in the concept phase.

Concept 3
Concept 3 is a Double Pipe Heat Exchanger in its simplest configuration. Double Pipe heat exchangers come in many shapes, sizes and configurations. Concept 3 will outline one of these configurations and its benefits.


Figure 6 3: Double Pipe heat Exchanger (Parallel Flow)

The Double Pipe heat exchanger is perhaps the simplest type of heat exchanger. The principle is such that one fluid flows through the center pipe of the heat exchanger and the other fluid in the annular space between the two pipes. In the case of figure 6-3 the cold fluid is flowing through the annular space between the two pipes and the hot fluid is flowing through the center pipe.

Double Pipe heat exchangers can be very large or very small depending on the size the application requires. The greatest advantage of the double pipe heat exchanger is the simple design. Double pipe heat exchangers can also operate in a true counter flow pattern that is the most efficient flow pattern possible.

Concept 4
Concept 4 is a Compact Heat Exchanger. Compact heat exchangers come in many shapes, sizes and configurations. Concept 4 will outline one of these configurations and its benefits.


Figure 6 4: Compact Heat Exchanger

The Compact heat exchanger is perhaps the heat exchanger with the largest heat transfer surface area per unit volume. Compact heat exchangers are design to maximise area per unit volume of fluid. The principle is such that one fluid flows through the flat surfaces of the heat exchanger and the other fluid in the pipes that are place perpendicular to the plates. In the case of figure 6-4 the cold fluid is flowing in the pipes and the hot fluid is flowing through the flat plate section of the heat exchanger.

Compact heat exchanger are design the maximise space. Hence compact heat exchanger are ideal for where space is restricted. Perhaps the greatest advantage of the double pipe heat exchanger is the high heat transfer coefficient. Compact heat exchanger are also less vulnerable to fouling and exhibit a low initial cost.

Concept 5
Concept 5 is a Plate Heat Exchanger. Plate heat exchangers come in many shapes, sizes. Concept 5 will outline its benefits.

Figure 6 5: Plate Heat Exchanger
A plate heat exchanger, also commonly known as plate and frame heat exchangers, consist of a series of plates with corrugated flat flow passages (Ghajar, 2007). The plate heat exchangers arranges the fluid flow in alternate flow passages. This results in each cold steam being surrounded by a two hot flow steams, resulting in very effective heat transfer.

Plate heat exchangers can be very large or very small depending on the size the application requires. The greatest advantage of the plate heat exchanger is that it requires a small footprint to operate in. Plate heat exchangers also have a low initial cost and are very easy to clean.

Advantages and Disadvantages
Refer to section 2.4 for a more detail explanation of the types of heat exchangers and also see Table 1 for all the advantages and disadvantages of the types of heat exchangers.

Concept Evaluation
The Concept evaluation phase of the design will evaluate the different concept base on the criteria mentioned in section 6.2.

Concept Scoring
The concept screening will screen all of the concepts to identify some concepts for further consideration. Concept 3 (Double Pipe Heat Exchanger) was selected as the Reference concept. All the concepts will be scored against the reference concept.

The rating system will be conducted as follow:

Relative Performance
Much Worse than Reference 1
Worse than Reference 2
Same as Reference 3
Better than Reference 4
Much Better than Reference 5

Concepts
Concept 1 Concept 2 Concept 3
(Reference)
Selection Criteria Weight Rating Weighted Score Rating Weighted Score Rating Weighted Score
Heat Removal Capability 15% 4 0.06 4 0.06 3 0.45
Reliability 15% 5 0.75 5 0.75 3 0.45
System Efficiency 15% 4 0.6 4 0.6 3 0.45
Safety 10% 4 0.4 4 0.4 3 0.3
Noise Generation 10% 3 0.3 3 0.3 3 0.3
Size 7.5% 2 0.15 2 0.15 3 0.225
Cost 7.5% 2 0.15 2 0.15 3 0.225
Manufacturability 7.5% 2 0.15 1 0.075 3 0.225
Maintenance 7.5% 3 0.225 2 0.15 3 0.225
Mass 5% 2 0.1 2 0.1 3 0.15
Total score 3.425 3.275 3.0
Rank 1 3 5
Continue? Develop No No

Concepts
Concept 4 Concept 5 Concept 3
(Reference)
Selection Criteria Weight Rating Weighted Score Rating Weighted Score Rating Weighted Score
Heat Removal Capability 15% 5 0.75 5 0.75 3 0.45
Reliability 15% 3 0.45 3 0.45 3 0.45
System Efficiency 15% 4 0.6 4 0.6 3 0.45
Safety 10% 2 0.2 2 0.3 2 0.3
Noise Generation 10% 3 0.3 3 0.3 3 0.3
Size 7.5% 4 0.3 4 0.3 3 0.225
Cost 7.5% 3 0.225 2 0.15 3 0.225
Manufacturability 7.5% 2 0.15 2 0.15 3 0.225
Maintenance 7.5% 2 0.15 1 0.075 3 0.225
Mass 5% 4 0.2 4 0.2 3 0.15
Total score 3.325 3.175 3.0
Rank 2 4 5
Continue? No No No

Concept Selection
The scores of each concept is very similar. Each concept excelled in one area more than the other, making each concept unique in its own way.

The concept scoring the highest overall points is concept 1 - Shell and Tube heat exchanger.

Detailed Concept

Conclusion
Shell and tube heat exchangers are the most common type of heat exchanger in industry and several codes and standards govern the design of this type of heat exchanger. Designing according to applicable standards will make this heat exchanger design very reliable, which is essential to the heat exchanger application for this project.

DETAILED DESIGN

Server Room Layout
The server room layout forms an important role in determining the air-conditioning layout. However the layout of the server room also has to comply with health and safety standards. According to SANS 10400 Section TT20.1 (a), the width of any escape route within any room having a population of more than 25 persons shall be not less than 800 mm (Standars, 2014). Also according to the OSHA (Occupational Safety and Health Association), in terms of industrial aisles, the aisle should be at least 1219.2mm (4 Feet) in width and be 914.4mm (3 Feet) wider than the largest equipment that has to pass through them (Labor, n.d.). The following layout was then selected complying with both standards. Dimensions are given in millimetres.


Figure 7 1: Server Room Layout
The layout equates to 176 racks, each containing 12 servers. Thus the total amount of servers in the room is 2112.

Chosen Racks
A server enclosure, on more commonly known in industry as a 'rack', is a structure designed to house multiple equipment modules. The chosen rack brand is for the server center is APC (American Power Conversion).

The chosen rack for the server room is a NetShelter SX 48U (AR3357) enclosure. The NetShelter SX 48U are high quality enclosures for industrial standard (EIA/ECA-310), 438mm rack mount hardware, which includes servers and other equipment.


Figure 7 2: NetShelter SX 48U (AR3357) enclosure ((APC), n.d.)

The dimension for the enclosure are as follow:
Height
2258mm
Width
750mm
Depth
1200mm

The Rack was chosen due based on the following criteria:
Maximizing airflow
Accommodates industrial standard servers
Easy Installation
Easy cable management.
Integrating power distribution features

The enclosures will be joined side to side and installed without side panels. Refer to Pg.15 of the Installation manual for further details.

The installed racks require a service clearance as follow.
Top Service Clearance
600mm
Back Service Clearance
1000mm
Front Service Clearance
1000mm ((APC), n.d.)


Figure 7 3: NetShelter SX 48U Service Clearance Schematic

Thermodynamic Calculations
Chiller
Condenser
Evaporator
Compressor
Pumps
Container and Mountings
Total Mass

CONTIGANCY DESIGN
All chilled water pump and AHU's will be on UPS and generator backup.

Must provide enough time to restart chillers. 10min according to facilitiesnet

MANUFACTURING ANALYSIS

Manufacturing Analysis

MAINTENANCE ANALYSIS

Maintenance Analysis

RELIABILITY ANALYSIS

Reliability Analysis

QUALIFICATION REQUIREMENTS

Qualifications Analysis

COST ANALYSIS

Cost of Standard Components
Cost of Materials
Total Cost

SOCIAL, LEGAL, HEALTH, SAFETY AND ENVIRONMENTAL IMPACTS

Social Impacts
Legal Impacts
Health Impacts
Safety Impacts
Environmental Impacts
Conclusion

DRAWINGS

Drawings

CONCLUSION AND RECOMMENDATIONS

Conclusion
Recommendations

REFERENCES
References
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