Trane trg-trc001-en - Manuals

TRG-TRC001-EN iii Contents period one The Psychrometric Chart ................................... 1 Properties of Air ......................................................... 2Constructing a Simple Psychrometric Chart .............. 8Effect of Sensible Heat and Moisture Changes ....... 15 period tw...

TRG-TRC001-EN 1 notes period one The Psychrometric Chart Psychrometry is the science dealing with the physical laws of air – water mixtures. When designing an air conditioning system, the temperature and moisture content of the air to be conditioned, and the same properties of the air needed to prod...

2 TRG-TRC001-EN notes period one The Psychrometric Chart Properties of Air At first glance, the psychrometric chart appears to be an imposing network of lines. When properly used, however, it provides valuable information about the properties of air. During this session, the psychrometric chart and ...

TRG-TRC001-EN 3 period one The Psychrometric Chart notes Dry-bulb temperatures are read from an ordinary thermometer that has a dry bulb. Wet-bulb temperatures are read from a thermometer whose bulb is covered by a wet wick. The difference between the wet-bulb temperature and the dry-bulb temperatur...

4 TRG-TRC001-EN notes period one The Psychrometric Chart The third property, dew-point temperature , is the temperature at which moisture leaves the air and condenses on objects, just as dew forms on grass and plant leaves. When the dry-bulb, wet-bulb, and dew-point temperatures are the same, the ai...

TRG-TRC001-EN 5 period one The Psychrometric Chart notes The fourth property, relative humidity , is a comparison of the amount of moisture that a given amount of air is holding, to the amount of moisture that the same amount of air can hold, at the same dry-bulb temperature. Relative humidity is ex...

6 TRG-TRC001-EN notes period one The Psychrometric Chart Finally, humidity ratio describes the actual weight of water in an air – water vapor mixture. In other words, if one pound of air were wrung completely dry, comparing the weight of the water to the weight of the dry air would yield its humidit...

8 TRG-TRC001-EN notes period one The Psychrometric Chart Notice that the point of intersection falls between two relative humidity curves: 40% and 50%. By interpolation, the relative humidity at this condition is approximately 47%. Constructing a Simple Psychrometric Chart To better understand the p...

TRG-TRC001-EN 9 period one The Psychrometric Chart notes These saturation points can be plotted on a chart with dry-bulb temperature along the horizontal axis and humidity ratio along the vertical axis. When several saturation points are plotted, the curve created resembles the relative humidity cur...

14 TRG-TRC001-EN notes period one The Psychrometric Chart The psychrometric chart now defines these five properties of air: dry-bulb temperature (vertical lines), humidity ratio and dew-point temperature (horizontal lines), relative humidity (curved lines) and wet-bulb temperature (diagonal lines). ...

TRG-TRC001-EN 15 period one The Psychrometric Chart notes Effect of Sensible Heat and Moisture Changes When either the sensible heat content or the moisture content of air changes, the point on the psychrometric chart that represents the original air condition moves to a position that represents the...

16 TRG-TRC001-EN notes period one The Psychrometric Chart On the other hand, if moisture is added to air without changing the dry-bulb temperature, the air condition moves upward along a dry-bulb temperature line. Finally, if moisture is removed from the air without changing its dry-bulb temperature...

TRG-TRC001-EN 17 period one The Psychrometric Chart notes Put all of these changes together on one chart and they show the direction the air condition will move when the dry-bulb temperature or moisture content is altered. In actual practice, however, both the dry-bulb temperature and moisture conte...

18 TRG-TRC001-EN notes Before an air conditioning problem can be analyzed on the psychrometric chart, the conditions of the air to be cooled or heated must be known. The air entering the cooling coil may be 100% recirculated ( A ), 100% outdoor ( B ), or a mixture of the two ( C ). 3V\FKURPHWU\ SHUL...

22 TRG-TRC001-EN notes period three Sensible Heat Ratio This period is devoted to understanding the term sensible heat ratio and how it is represented on the psychrometric chart. The ratio of sensible heat gain to total heat gain is one of the most important factors affecting air conditioning system...

24 TRG-TRC001-EN notes period three Sensible Heat Ratio Imagine conditioned supply air as a sponge. As it enters a room, it absorbs heat and moisture. The amount of heat and moisture absorbed depends on the temperature and humidity of the supply air. This “sponge,” the supply air, must be cool enoug...

26 TRG-TRC001-EN notes period three Sensible Heat Ratio This relationship between the conditions and quantity of the supply air can be described using the analogy of maintaining a constant temperature within a container of water. In this illustration, the container of water is capable of absorbing h...

TRG-TRC001-EN 27 period three Sensible Heat Ratio notes The sensible heat ratio , abbreviated as SHR, refers to the comparison of sensible heat gain to total heat gain (sensible heat plus latent heat). Once this ratio is known, an SHR line can be drawn on the psychrometric chart. A scale around the ...

30 TRG-TRC001-EN notes period four Air Quantity Next, we will determine the flow rate of supply air necessary to maintain a given set of design room conditions. Before proceeding, one more set of curves on the psychrometric chart must be identified. These curved lines represent the changes in dry-bu...

TRG-TRC001-EN 35 period four Air Quantity notes For this example, the supply airflow is calculated as follows: The cooling coil must cool and dehumidify 3,430 cfm of air from the entering condition C to the supply air condition D to maintain the desired room conditions. %WXKU Õ ƒ) ¤ ƒ) FIP 67(36ROYH...

TRG-TRC001-EN 37 notes period five Tons of Refrigeration The psychrometric chart can also be used to determine the total load on the refrigeration equipment, expressed in Btu per hour or tons of refrigeration . One ton equals 12,000 Btu/hr. Another property of air, enthalpy, must now be defined. Ent...

38 TRG-TRC001-EN notes period five Tons of Refrigeration Using the previous example for calculating supply airflow, the first step is to determine the enthalpies of the air entering and leaving the cooling coil. This is accomplished by lining up three points on the chart, including the entering-air ...

TRG-TRC001-EN 39 period five Tons of Refrigeration notes Realize that 4.5 is not a constant! It is the product of density of air and the conversion factor of 60 minutes per hour. The density of air at “standard” conditions (69.5 °F DB dry air at sea level) results in the value 4.5. Air at other cond...

42 TRG-TRC001-EN notes period six Psychrometric Analyses Now we will look at a few ways that the psychrometric chart can help us analyze air conditioning systems. For simplicity, we will limit our examples to systems serving a single zone. In the previous example, the sensible heat ratio was based o...

TRG-TRC001-EN 45 period six Psychrometric Analyses notes This is the manner in which a constant-volume, variable-temperature system with a modulating coil performs. It provides a constant quantity of air to the room and responds to part-load conditions by varying the supply air temperature. This is ...

TRG-TRC001-EN 49 period six Psychrometric Analyses notes This supply air E mixes with room air along the part-load 0.70 SHR line, arriving at the resulting new room conditions A’ . While the quantity and temperature of supply air are suitable to absorb the room’s sensible heat gain, they are unable ...

52 TRG-TRC001-EN notes Let’s review some of the main concepts from this clinic on psychrometry. The lines of the psychrometric chart represent five physical properties of air: dry bulb, wet bulb, dew point, humidity ratio, and relative humidity . If any two of these properties are known, the remaini...

TRG-TRC001-EN 53 period seven Review notes In Period Two, a method was discussed to determine the resulting properties of an air mixture. By plotting the conditions of the outdoor air and recirculated air , and using the percentage of outdoor air, the resulting condition of the air mixture was calcu...

TRG-TRC001-EN 57 Questions for Period 1 1 Given air conditions of 80 °F DB and 60% RH, find the humidity ratio and dew-point temperature. 2 Given air conditions of 85 °F DB and a humidity ratio of 90 grains/lb, find the relative humidity and wet-bulb temperature. 3 Given air conditions of 74 °F WB a...

58 TRG-TRC001-EN Quiz Questions for Period 4 9 Given a room with a 42,000 Btu/hr sensible heat gain and a 56,000 Btu/hr total heat gain (excluding ventilation heat gain); and indoor design conditions of 80 °F DB and 50% RH: a Determine the sensible heat ratio. b Draw the SHR line. 10 Given a room wi...

TRG-TRC001-EN 59 1 93 grains/lb, 64.8 °F DP 2 49.5% RH, 70.5 °F WB 3 85 °F DB, 110 grains/lb 4 41% RH, 64 °F WB 5 56 °F DP, 32% RH 6 a 95 °F × 0.20 = 19 °F80 °F × 0.80 = 64 °FMixed-Air Temperature = 19 °F + 64 °F = 83 °F b See Figure 90. c 69.4 °F WB 7 a 95 °F × 0.15 = 13.5 °F78 °F × 0.85 = 66.3 °FM...

64 TRG-TRC001-EN ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers coil curves These represent the changes in dry-bulb and wet-bulb temperatures as air passes through a “typical” cooling coil. constant-volume system A type of air-conditioning system that varies the tem...