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Outdoor air is mixed with room return air to reduce the refrigeration load on a cooling coil. (a) For a space condition of 77 F (25 C) db and 68 F (20 C) wb, describe the maximum wet bulb and dry bulb temperatures that will reduce the coil load. (b) Suppose a system is designed to supply 10,300 cfm (5 m3/s) at 64 F (18 C) db and 63 F (17 C) wb to a space maintained at the conditions given in part (a) above. What amount of outdoor air at 68 F (20 C) db and 90 percent relative humidity can be mixed with the return air if the coil SHF is 0.6? (c) What is the apparatus dew point in part (b) above? (d) Compare the coil refrigeration load in part (b) above with the outdoor air to that without outdoor air. Assume sea-level pressure.
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Chapter 3 Solutions
Heating Ventilating and Air Conditioning: Analysis and Design
- An engineer has been given the following data on a conditioned room: Sensible heat gain 30 kW Latent heat gain 15 kW Supply air 18°C Outdoor air 35°C DB and 24°C WB Desired room condition 27°C DB and 50% RH For ventilation, 15% is outdoor air, the balance of air requirement being recirculated from room conditioned with some portion being by-passed around the cooling coil. There is no reheater, the desired room state is attained by the by-passing of air. It is found that the apparatus DP temperature of coil is 10°C. Find the: a. tons of refrigeration; and b. mass flow rate of the time by-passed air.arrow_forward1. Moist air enters a refrigeration coil at 89 F dry-bulb temperature and 65 F thermodynamic wet bulb temperature at a rate of 14oo cu ft per min. The surface temperature of the coil is 55 F . If 3.5 tons of refrigeration are available, find the dry bulb and wet bulb temperatures of the air leaving the coil. Assume sea level pressure.arrow_forwardT-8arrow_forward
- Solve it using the chat and show how you get the answers from the chatarrow_forwardThe following data refer to summer air conditioning of a building: Outside design conditions 43 °C DBT, 27 °C WBT Inside design condition 25 °C DBT, 50% RH Room sensible heat gain 84000 kJ/h Room latent heat gain 21000 kJ/h BPF of cooling coil 0.2 The return air from the room is mixed with the outside air before entry to cooling coil in the ratio of 4:1 by mass. Determine: (a) Apparatus dew point of the cooling coil (b) Entry and exit conditions of air for cooling coil (c) Fresh air mass flow rate and (d) Refrigeration load on the cooling coil.arrow_forwardProblem 5.7 For air-conditioning system operation in cold weather, it is possible to introduce enough outdoor air to eliminate cooling by the air conditioner. This is called an economizer, and the control strategy is to vary the amount of outdoor air entering a plenum so that the outlet state is at the set point. For zone conditions of 75 F and 50 % and a constant circulating air flow rate of 25,000 cfm, determine the outdoor and return air flow rates necessary to maintain a 55 F supply air leaving the plenum. The outdoor air temperature varies between 10 F and 50 F and the relative humidity is always 30 %. Draw some conclusions from your results.arrow_forward
- A 72 tons refrigeration system is used to produce chilled water from 20 ° C to 4 ° c. determine the volume flow of waterarrow_forward1arrow_forwardRefrigeration system Reminder: Present step by step solution. If EB in to be used, start in System Under Study, then, Fluid Under Study, and draw BED.arrow_forward
- An ammonia compressor has a volumetric efficiency of 85%, operating condensing & evaporating temperatures of 40 C & 10 C respectively for a cooling capacity of 10 tons with compression index of 1.2, mean piston speed of 2 m/s, 5% clearance & bore to stroke ratio of 0.7. Determine the following 1. Draw the PH Diagram indicating the temperatures, enthalpies & initial specific volume 2. Refrigerating Effect in kJ/kg 3. Mass flow rate in kg/sarrow_forwardAn ideal gas at 15 lbf/in2, 77°F flows horizontally at 516 ft/s into an adiabatic diffuser. It exits at 28 ft/s. Assume the heat capacity of the gas is constant.a. Determine the change in specific enthalpy (in Btu/lbm) and the outlet temperature if the gas is He.b. Repeat for R-125.c. Repeat for ozone (O3), which has a Molecular Mass of 47.9982 and a Cv0 of 0.1538 Btu/(lbm∙°R).arrow_forwardQ1: An engineer claimed that his device produces two streams of 1 am air (outlet 1) and 1.5 atm (outlet 2) at temperatures of 460 °R and 635 °R, respectively, if he enters 530 °R of the air at 5.1 atm. If the ratio of outlet 2 to outlet 1 is 0.6, justify the engineer's claim. Assume ideal gas process with a constant heat capacity of 0.24 Btu/lb.°R.arrow_forward
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