Details and Descriptions

Graphic and Image descriptions

Fig. A1 Psychrometric Process for Computer Room A/C Units with Dry Coil Operation, Appendix A, Section A3.1

Figure A1 depicts dry coil operation. Air enters the cooling coil at condition R and leaves the coil at condition C. It mixes with bypass air at condition R to form a mixture at condition M. There is a temperature rise of 1.5 °C between the coil and the entry into the room, hence it enters the room at condition S. All of these processes occur at constant sensible heat ratio of 1.0, therefore the psychometric process follows a horizontal line R-S-M-C.

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Fig. A2 Psychrometric Process for Computer Room A/C Unit with Wet Coil Operation, Appendix A, Section A3.1

Figure A2 describes the processes that occur if there is wet coil operation - i.e. if condensation occurs at the coil. Since there is condensation, the psychometric process no longer follows a horizontal line, and the air leaves the coil at condition C1. There is a change in enthalpy between conditions C and C1, depicted as LHc in Figure A2. Air is now supplied at condition S1, and it has to return to condition R during the cooling process. Hence, the psychometric process follows the horizontal line (at constant SHF), and then an enthalpy change is required to return to condition R from R1. This is shown as LHh. Thus, it is seen that two enthalpy changes are required, LHc and LHh, so there is, in effect, a double penalty on the cooling system.

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Fig. A3 Chilled Water or Glycol-cooled Computer Room A/C Units, Appendix A, Section A.4.3

Figure A3 shows one possible arrangement, with a heat recovery device. The dry cooler heat exchanger is provided for free cooling and energy conservation. The cooling coil controls should include 3-way valves (an air cool chiller unit, a filling funnel and a dry cooler heat exchanger) to ensure adequate flow through the chiller at all times. This system is used when the distances between condenser and compressor are too great for the use of refrigerant cooled unit. It is a relatively maintenance free system.

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Fig. A4 Heat Recovery System for use with Glycol-cooled Condensers, Appendix A Section A5.0

Figure A4 shows how the domestic water heater and the condenser are arrange to recover the heat for heating domestic water. When T-1 calls for heat, glycol is drawn through the heat recovery loops, circulating pump P-1. The flow varies through the modulating Valve V-1 bypass.

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Fig. A5 Energy Conservation – Additional Cooling Coil to Utilize Condenser Fluid, Appendix A, Section A 5.4

Figure A5 shows how to divert the condenser fluid from the refrigerant condenser to an additional cooling coil in the A/C unit. The fluid is emptied in the filling funnel which leads to an expansion tank, which is cooled down by the dry cooler heat exchanger. The glycol condenser pump is activated and enables V-1 to activate energy conservation with additional cooling coil to utilize condenser fluid.

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