Trane TRG-TRC003-EN - Manuals

TRG-TRC003-EN iii Contents period one Heat and Refrigeration ....................................... 1 What is Heat? ......................................................... 2 Principles of Heat Transfer ...................................... 4 period two Refrigerants .................................

TRG-TRC003-EN 1 notes period one Heat and Refrigeration Before discussing the refrigeration system, we need to understand the terms heat and refrigeration. The term refrigeration is commonly associated with something cold. A household refrigerator, for example, keeps food cold. It accomplishes this ...

2 TRG-TRC003-EN notes period one Heat and Refrigeration What is Heat? Heat is a form of energy. Every object on earth contains heat energy in both quantity and intensity. Heat intensity is measured by its temperature, commonly in either degrees Fahrenheit (°F) or degrees Celsius (°C). If all heat we...

TRG-TRC003-EN 3 period one Heat and Refrigeration notes These two different masses of water contain the same quantity of heat, yet the temperature of the water on the left is higher. Why? The water on the left contains more heat per unit of mass than the water on the right. In other words, the heat ...

4 TRG-TRC003-EN notes period one Heat and Refrigeration Principles of Heat Transfer Air-conditioning and refrigeration systems use the principles of heat transfer to produce cooling and heating. The three principles discussed in this clinic are: ■ Heat energy cannot be destroyed; it can only be tran...

6 TRG-TRC003-EN notes period one Heat and Refrigeration The third principle is that heat is transferred from one substance to another by one of three basic processes: conduction, convection, and radiation. The device shown is a baseboard convector that is commonly used for heating a space. It can be...

8 TRG-TRC003-EN notes period one Heat and Refrigeration In the English system of units, there is a larger and more convenient measure of the rate of heat flow. It is called a ton of refrigeration . One ton of refrigeration produces the same cooling effect as the melting of 2000 lb of ice over a 24-h...

TRG-TRC003-EN 9 notes In this period we will discuss refrigerants, the substances used to absorb and transfer heat for the purpose of cooling. Ice can be used to preserve food. Because heat flows from a higher temperature substance to a lower temperature substance, ice can be used in a frozen displa...

TRG-TRC003-EN 11 period two Refrigerants notes Finally, Refrigerant-22 (R-22) is a chemical used in many refrigeration systems. If, hypothetically, an open container of liquid R-22 were placed in the frozen display case, when exposed to atmospheric pressure, it would absorb heat and boil violently a...

14 TRG-TRC003-EN notes period two Refrigerants The quantity of heat that must be added to the water in order for it to evaporate cannot be sensed by an ordinary thermometer. This is because both the water and steam remain at the same temperature during this phase change. This kind of heat is called ...

TRG-TRC003-EN 15 period two Refrigerants notes have different capacities for absorbing heat. This capacity is a property of the substance called specific heat. Suppose equal quantities of two different liquids, $ and % , both at room temperature, are heated. The gas burners are lighted and adjusted ...

16 TRG-TRC003-EN notes period two Refrigerants Modern Refrigerants Refrigerants are substances that are used to absorb and transport heat for the purpose of cooling. When selecting a refrigerant to use for a given application, in addition to these heat transfer properties the manufacturer considers ...

TRG-TRC003-EN 17 notes period three Refrigeration Cycle The frozen display case example used in the last period demonstrates that, at a given pressure, refrigerants absorb heat and change phase at a fixed temperature. It also shows how these refrigerants are “consumed” in the cooling process, either...

20 TRG-TRC003-EN notes period three Refrigeration Cycle At higher pressures, refrigerant boils and condenses at higher temperatures. This can be explained by examining the properties of water. At atmospheric pressure (14.7 psia [0.10 MPa]), water boils and evaporates at 212 °F [100 °C]. When pressur...

TRG-TRC003-EN 21 period three Refrigeration Cycle notes increase the pressure of the resulting refrigerant vapor to 280 psia [1.93 MPa]. This increase in pressure raises the temperature at which the vapor would condense back into liquid to 121.5 °F [49.7 °C]. In order to condense the refrigerant vap...

22 TRG-TRC003-EN notes period three Refrigeration Cycle Basic Refrigeration System This diagram illustrates a basic vapor-compression refrigeration system that contains the described components. First, notice that this is a closed system. The individual components are connected by refrigerant piping...

TRG-TRC003-EN 23 period three Refrigeration Cycle notes At the inlet to the evaporator , the refrigerant exists as a cool, low-pressure mixture of liquid and vapor. In this example, the evaporator is a finned-tube coil used to cool air. Other types of evaporators are used to cool water. The relative...

24 TRG-TRC003-EN notes period three Refrigeration Cycle The condenser is a heat exchanger used to reject the heat of the refrigerant to another medium. The example shown is an air-cooled condenser that rejects heat to the ambient air. Other types of condensers are used to reject heat to water. The h...

TRG-TRC003-EN 25 period three Refrigeration Cycle notes The high-pressure liquid refrigerant ( ' ) flows through the expansion device, causing a large pressure drop. This pressure drop reduces the refrigerant pressure, and, therefore, its temperature, to that of the evaporator. At the lower pressure...

26 TRG-TRC003-EN notes period four Pressure–Enthalpy Chart During this period we will again analyze the basic vapor-compression refrigeration cycle. However, this time we will use a graphic tool called the pressure–enthalpy chart. The pressure–enthalpy (P- h ) chart plots the properties of a refrige...

TRG-TRC003-EN 27 period four Pressure–Enthalpy Chart notes envelope, the refrigerant exists as a mixture of liquid and vapor. If the enthalpy of the refrigerant lies to the right of the envelope, the vapor is superheated . Similarly, if the enthalpy of the refrigerant lies to the left of the envelop...

28 TRG-TRC003-EN notes period four Pressure–Enthalpy Chart The distance between the edges of the envelope indicates the quantity of heat required to transform saturated liquid into saturated vapor at a given pressure. This is called the heat of vaporization . For example, B represents the enthalpy o...

TRG-TRC003-EN 29 period four Pressure–Enthalpy Chart notes At the inlet to the evaporator, the refrigerant is at a pressure of 85 psia[0.59 MPa] and a temperature of 41.2 °F [5.1 °C], and is a mixture of liquid and vapor (mostly liquid). This cool, low-pressure refrigerant enters the evaporator ( $ ...

30 TRG-TRC003-EN notes period four Pressure–Enthalpy Chart The compressor draws in the superheated refrigerant vapor ( & ) and compresses it to a pressure and temperature ( ' ) high enough that it can reject heat to another fluid. As the volume of the refrigerant is reduced by the compressor, it...

TRG-TRC003-EN 31 period four Pressure–Enthalpy Chart notes temperature is 121.5 °F [49.7 °C]. The refrigerant vapor leaving the compressor is therefore 70 °F [38.9 °C] above its saturation temperature. This hot, high-pressure refrigerant vapor then travels to the condenser. Inside of the condenser, ...

TRG-TRC003-EN 35 notes We will now review the main concepts that were covered in this clinic reagrding the vapor-compression refrigeration cycle. Period One introduced the concept of heat and how it is transferred from one substance to another. Recall that heat is a form of energy and can vary in bo...

38 TRG-TRC003-EN notes period five Review For more information, refer to the following references: ■ Trane Air Conditioning Manual ■ Trane Reciprocating Refrigeration Manual ■ ASHRAE Handbook – Fundamentals ■ ASHRAE Handbook – Refrigeration ■ ASHRAE Handbook – Systems and Equipment Visit the ASHRAE ...

TRG-TRC003-EN 39 Questions for Period 1 1 Heat intensity is measured in terms of its __________? 2 Heat quantity is measured with units of __________? 3 Heat always flows from a substance of ________ (higher, lower) temperature to a substance of ________ (higher, lower) temperature. 4 What are the t...

40 TRG-TRC003-EN Quiz 10 What is the state of the refrigerant when it enters the compressor? 11 What is the state of the refrigerant when it enters the expansion device? Questions for Period 4 12 What is enthalpy? 13 Using the pressure–enthalpy chart in Figure 59, identify the components of the vapo...

42 TRG-TRC003-EN 1 Temperature or degrees Fahrenheit [degrees Celsius] 2 British Thermal Unit (Btu) [kilocalorie (kcal) or kiloJoule (kJ)] 3 Higher to lower 4 Conduction, convection, and radiation 5 Boiling the water requires more energy–970.3 Btu/lb [244.5 kJ/kg]. Raising the temperature of the wat...

44 TRG-TRC003-EN ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers British Thermal Unit (Btu) A measure of heat quantity, defined as the quantity of heat energy required to change the temperature of 1 lb of water by 1 °F. compressor A mechanical device in the refrigera...