Trane trg-trc005-en - Manuals

TRG-TRC0 05-EN iii Contents Introduction ........................................................... 1 period one Refrigeration Cycle .............................................. 2 period two Condensers ............................................................ 5 Air-Cooled Condensers .............

TRG-TRC0 05-EN 1 notes Introduction The major components of a vapor-compression refrigeration system include the compressor, condenser, expansion device, and evaporator. The latter three will be discussed in this clinic — the compressor is discussed in a separate clinic. This clinic will also discus...

2 TRG-TRC0 05-EN notes period one Refrigeration Cycle First, a brief review of the vapor-compression refrigeration cycle will help to relate these components. A diagram of a typical vapor-compression refrigeration cycle can be superimposed on a pressure-enthalpy (P- h ) chart to demonstrate the func...

TRG-TRC0 05-EN 5 notes The first major component to be discussed is the condenser. The condenser is a heat exchanger that rejects heat from the refrigerant to air, water, or some other fluid. The three common types of condensers are air-cooled, water-cooled, and evaporative. Air-Cooled Condensers A ...

6 TRG-TRC0 05-EN notes period two Condensers The air-cooled condenser is very popular in both residential and commercial applications because of its convenience. It requires very little maintenance and does not require the freeze protection and water treatment that is necessary with a water-cooled c...

TRG-TRC0 05-EN 7 period two Condensers notes An alternative air-cooled condenser uses a centrifugal fan to draw or blow air over the condensing coil. The principal advantage of this design is that the centrifugal fan is capable of overcoming the higher static-pressure losses associated with ductwork...

8 TRG-TRC0 05-EN notes period two Condensers causing the refrigerant vapor within the tubes to condense. The remaining water then falls to the sump to be recirculated and used again. Subcooling of the refrigerant can be accomplished by piping the condensed liquid back through another few rows of coi...

TRG-TRC0 05-EN 9 period two Condensers notes A cooling tower is a device commonly used to cool condensing water. In this design, warm water is sprayed over the fill inside the cooling tower while a propeller fan draws outdoor air upward through the fill. The movement of air through the spray causes ...

10 TRG-TRC0 05-EN notes period two Condensers Condenser Control The heat rejection capacity of a condenser is influenced by (1) the temperature difference between the refrigerant and the cooling media (air, water, or other fluid), (2) the flow rate of the cooling media through the condenser, and (3)...

TRG-TRC0 05-EN 11 period two Condensers notes A reduction in condensing pressure lessens the power required to compress the refrigerant. Unfortunately, if the condensing pressure falls too low, the expansion valve may not be able to produce the flow of liquid refrigerant needed to satisfy the demand...

12 TRG-TRC0 05-EN notes period two Condensers It is more common, however, for a water-cooled condenser to be connected to a cooling tower. In this case, typical methods for modulating the water flow through the condenser include either using a variable-speed drive on the condenser water pump or usin...

TRG-TRC0 05-EN 13 period two Condensers notes Common methods of modulating this water temperature include controlling the cooling tower fans or using a cooling-tower bypass pipe. Controlling the cooling tower fans, either by cycling fans on and off or by using a variable-speed drive on the fans, all...

14 TRG-TRC0 05-EN notes period two Condensers A common method of controlling the capacity of an air-cooled condenser is to vary the airflow across the condenser coil. The heat-rejection rate of a multiple-fan condenser is often controlled by cycling fans on and off to maintain acceptable condensing ...

16 TRG-TRC0 05-EN notes period three Evaporators The second major component to be discussed is the evaporator . The evaporator is a heat exchanger that transfers heat from air, water, or some other fluid to the cool liquid refrigerant. Two common types of evaporators are the finned-tube and the shel...

TRG-TRC0 05-EN 17 period three Evaporators notes The fins of the coil are formed to produce turbulence as the air passes through them. This turbulence enhances heat transfer, preventing stratification within the coil-leaving airstream. To provide uniform heat transfer throughout the coil, the liquid...

18 TRG-TRC0 05-EN notes period three Evaporators Each distributor has an allowable range of refrigerant flow rates that define its stable operating range. As the size of the evaporator coil increases, it may be necessary to use more than one distributor to feed liquid refrigerant to the coil. Inside...

20 TRG-TRC0 05-EN notes period three Evaporators Evaporator Control The rate of heat exchange within an evaporator is governed by (1) the temperature difference between the refrigerant and the air or water being cooled, (2) the flow rate of the air or water through the evaporator, and (3) the flow r...

TRG-TRC0 05-EN 21 period three Evaporators notes Typically, an expansion valve is used to control the flow rate of refrigerant through the evaporator to maintain the proper amount of superheat, ensuring that the liquid refrigerant will be completely vaporized. Working in conjunction with the unloadi...

22 TRG-TRC0 05-EN notes period three Evaporators The face-split coil configuration, also called horizontal-split or parallel-flow, is split into parallel sections. A portion of the air passes through the top section, the remainder passes through the bottom section, and the two airstreams mix downstr...

TRG-TRC0 05-EN 23 period three Evaporators notes The intertwined coil configuration splits the coil sections by alternating the tubes fed in each row between two distributors. At lower loads, liquid refrigerant is fed to every other tube of the coil and, therefore, it behaves like a coil with substa...

24 TRG-TRC0 05-EN notes period three Evaporators Finally, the row-split coil configuration, also called vertical-split or series-flow, places the independently-controlled coil sections in series in the airstream. All of the air passes through both coil sections, one before the other. Typically, the ...

26 TRG-TRC0 05-EN notes period four Expansion Devices The final major component to be discussed is the expansion device. An expansion device is used to maintain a pressure difference between the high-pressure (condenser) and low-pressure (evaporator) sides of the system established by the compressor...

TRG-TRC0 05-EN 27 period four Expansion Devices notes In addition to maintaining a pressure difference, the thermostatic expansion valve controls the quantity of liquid refrigerant entering the evaporator. It ensures that the refrigerant will be completely vaporized within the evaporator ( A ) and m...

28 TRG-TRC0 05-EN notes period four Expansion Devices On the other hand, if too much liquid refrigerant enters the evaporator, not all of it will be vaporized. As a result, some liquid refrigerant gets into the compressor suction line. Since the compressor is designed to compress vapor and not liqui...

30 TRG-TRC0 05-EN notes period four Expansion Devices In a typical TXV application, the outlet of the valve is connected to the distributor. A remote bulb is attached to the suction line, where it senses the refrigerant vapor temperature leaving the evaporator. This bulb is charged with refrigerant ...

TRG-TRC0 05-EN 33 period four Expansion Devices notes A typical recommended superheat setting is from 8 to 12 °F [4.4 to 6.7 °C]. Too little superheat is risk y because it presents a danger of allowing refrigerant to leave the evaporator in the liquid state. As mentioned earlier, the compressor is d...

34 TRG-TRC0 05-EN notes period five Accessories This period discusses several accessories used in comfort-cooling refrigeration systems. Solenoid Valve A solenoid valve is used to stop the flow of refrigerant within the system. These valves are magnetically operated, and an electric winding controls...

36 TRG-TRC0 05-EN notes period five Accessories When the compressor is shut off, the evaporator contains a large quantity of liquid refrigerant. This can present a problem if some of the refrigerant drains into the suction line and slugs the compressor when it starts up again. To prevent this from o...

TRG-TRC0 05-EN 37 period five Accessories notes act as a catalyst in chemical reactions that result in the formation of acids. These acids can corrode system components and cause the oil to sludge. The filter drier should be installed close to the solenoid valve to provide the most protection for th...

38 TRG-TRC0 05-EN notes period five Accessories Moisture-Indicating Sight Glass A moisture-indicating sight glass is installed in the liquid line, upstream of the expansion valve, and permits the operator to observe the condition of the refrigerant prior to entering the expansion valve. The value of...

TRG-TRC0 05-EN 39 period five Accessories notes Suction Line Filter Similar to the liquid-line filter drier, the suction line filter performs the task of removing foreign matter from the refrigeration system. It is installed in the suction line, just upstream of the compressor. The suction filter co...

40 TRG-TRC0 05-EN notes period five Accessories Replaceable core suction filters are commonly installed after a compressor failure has occurred. The core is replaced after the foreign matter or acid has been removed from the system. Additionally, suction filters should be installed in all field-asse...

TRG-TRC0 05-EN 41 period five Accessories notes Shutoff Valve Shutoff valves are used to isolate one part of the refrigeration system from the rest. Additionally, they can be used to trap the refrigerant charge in one component of the system, the condenser for example, to permit service or repair to...

42 TRG-TRC0 05-EN notes period five Accessories Access Port An access port is used to add refrigerant to the system or for measurement. An access port is typically installed in the liquid line in a convenient location and is used to charge the system with liquid refrigerant. It is also used to measu...

TRG-TRC0 05-EN 43 notes We will now review the main concepts that were covered in this clinic about the components in a vapor-compression refrigeration system. Period One reviewed the vapor-compression refrigeration cycle using the P- h chart. A cool, low-pressure mixture of liquid and vapor refrige...

44 TRG-TRC0 05-EN notes period six Review of the refrigerant vapor causes it to desuperheat, condense into liquid, and further subcool before leaving the condenser ( D ) for the expansion device. Finally, the high-pressure liquid refrigerant flows through the expansion device, causing a large pressu...

TRG-TRC0 05-EN 45 period six Review notes Period Three presented the different types of evaporators and methods of evaporator control. The evaporator transfers heat from air, water, or some other fluid to the cool liquid refrigerant. The two common types of evaporators are finned-tube and shell-and-...

46 TRG-TRC0 05-EN notes period six Review Period Five discussed several accessories commonly used in comfort-cooling applications, including: solenoid valve, liquid-line filter drier, moisture-indicating sight glass, suction line filter, hot gas muffler, shutoff valve, and access port. The solenoid ...

48 TRG-TRC0 05-EN Questions for Period 1 1 Using the pressure–enthalpy chart in Figure 68, which two points correspond to superheating the refrigerant vapor inside the evaporator? 2 Again using Figure 68, which two points correspond to subcooling the liquid refrigerant inside the condenser? Question...

TRG-TRC0 05-EN 49 Quiz Questions for Period 4 10 What are the two primary purposes of a thermostatic expansion valve? 11 What are the risks of too much superheat in the system? Questions for Period 5 12 During a pump-down cycle, the compressor pumps the refrigerant from the _____ (low or high)-press...

50 TRG-TRC0 05-EN 1 B to C 2 F to G 3 Air-cooled, evaporative, and water-cooled 4 A decrease in system load and a reduction in the outdoor air temperature 5 Varying the airflow through the condenser coil or flooding the condenser coil with liquid refrigerant 6 A distributor 7 To direct the water in ...

TRG-TRC0 05-EN 51 access port A device that allows a technician to gain access to the refrigeration system for charging or measurement. air-cooled condenser A type of condenser where refrigerant flows through the tubes and rejects heat to air that is drawn across the tubes. ASHRAE American Society o...