Heating Ventilating and Air Conditioning: Analysis and Design
6th Edition
ISBN: 9780471470151
Author: Faye C. McQuiston, Jeffrey D. Spitler, Jerald D. Parker
Publisher: Wiley, John & Sons, Incorporated
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Textbook Question
Chapter 3, Problem 3.15P
Air enters a cooling coil at the rate of 5000 cfm (2.4 m3/s) at 80 F (27 C) db, 68 F (20 C) wb and sea-level pressure. The air leaves the coil at 55 F (13 C) db, 54 F (12 C) wb. (a) Determine the SHF and the apparatus dew point. (b) Compute the total and sensible heat transfer rates from the air.
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Air enters a cooling coil at the rate of 5000 cfm (2.4 m3/s) at 80 F (27 C). db, 68 F (20 C) wb and sea-level pressure. The air leaves the coil at 55 F (13
C) db, 54 F (12 C) wb. (a) Determine the SHF and the apparatus dew point.
(b) Compute the total and sensible heat transfer rates from the air.
0.2 A condenser condenses 2700kg steam per hour while air leaks into
It at 2.2kg/hr. The condensate and air suction spout temperatures
are 32.9°C. The barometer and vacuum gauge readings are
765mmHg and 690mmHg respectively. The condenser uses
125.55M9 of cooling water per hour to condense steam with a
dryness fraction of 0.86 and the air pump has a volumetric efficiency
of 82.5%. Take R = 0.287kJ/kgK for air and calculate:
%3D
6.2.1 the temperature rise of the cooling water (10.85°C);
6.2.2 the air pump capacity in m2/min (0.78m3³/min).
Moist air enters an air-conditioning system as shown in the figure below at T1 = 28°C, 01 = 80% and a volumetric flow rate of (AV)1 =
0.47 m3/s. At the exit of the dehumidifying section, the air is saturated, @, = 100%, and the condensate leaves this section at the same
temperature as the moist air. At the exit of the heating section the moist air is at T3 = 24°C, 03 = 50%. The system operates at steady
state, the pressure is 1 bar at all locations, and kinetic and potential energy effects are negligible.
Dehumidifying
Section
Heating
Section
2 = 100%
T3 = 24°C
Ø3
= 50%
T1= 28°C
$1. (AV)ı
Initial dew
point-
O = 100%
Condensate -
saturated at T2
T2
T3
ww
Chapter 3 Solutions
Heating Ventilating and Air Conditioning: Analysis and Design
Ch. 3 - A space is at a temperature of 75 F (24 C), and...Ch. 3 - Determine the humidity ratio, enthalpy, and...Ch. 3 - Suppose the air of Problem 3-2 is at a pressure...Ch. 3 - What is the enthalpy of moist air at 70 F (20 C)...Ch. 3 - The inside surface temperature of a window in a...Ch. 3 - What is the mass flow rate of dry air flowing at a...Ch. 3 - Determine the dew point of moist air at 80 F (27...Ch. 3 - A room is to be maintained at 72 F (22 C) db. It...Ch. 3 - Air is cooled from 80 F db and 67 F wb until it is...Ch. 3 - Conditions in a room are measured to be 80 F db...
Ch. 3 - The environmental conditions in a room are to be...Ch. 3 - Air enters a cooling coil at the rate of 5000 cfm...Ch. 3 - Air flowing in a duct has dry and wet bulb...Ch. 3 - Air is humidified with the dry bulb temperature...Ch. 3 - Air at 38 C db and 20 C wb is humidified...Ch. 3 - Two thousand cfm (1.0 m3/s) of air at an initial...Ch. 3 - Air at 40 F (5 C) db and 35 F (2 C) wb is mixed...Ch. 3 - Rework Problem 3-25, using Chart 1a, with the...Ch. 3 - The design cooling load for a zone in a building...Ch. 3 - Assume that the air in Problem 3-22 is supplied to...Ch. 3 - The sensible heat loss from a space is 500,000...Ch. 3 - Air enters a refrigeration coil at 90 Fdb and 75...Ch. 3 - A building has a total heating load of 200,000...Ch. 3 - Reconsider Problem 3-36 for an elevation of 5000...Ch. 3 - The system of Problem 3-34 has a supply air fan...Ch. 3 - An evaporative cooling system is to be used to...Ch. 3 - A cooling system is being designed for use at high...Ch. 3 - Consider a space heating system designed as shown...Ch. 3 - A variable-air-volume VAV cooling system is a type...Ch. 3 - Rework Problem 3-43 for an elevation of 5000 feet...Ch. 3 - The design condition for a space is 77 F (25 C) db...Ch. 3 - Rework Problem 3-45 for an elevation of 5000 feet...Ch. 3 - It is necessary to cool and dehumidify air from 80...Ch. 3 - Conditions in one zone of a dual-duct conditioning...Ch. 3 - Rework Problem 3-48 for an elevation of 5000 ft...Ch. 3 - A water coil in Problem 3-48 cools return air to...Ch. 3 - A multizone air handler provides air to several...Ch. 3 - Under normal operating conditions a zone has a...Ch. 3 - An interior zone of a large building is designed...Ch. 3 - Outdoor air is mixed with room return air to...Ch. 3 - Consider an enclosed swimming pool. The pool area...Ch. 3 - One particular zone served by a multizone air...Ch. 3 - A research building requires 100 percent outdoor...Ch. 3 - A space requires cooling in the amount of 120,000...
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- 1. A variable-air-volume cooling system delivers air to a controlled space maintained at 24 C db and 17 C wb. Under design conditions, the total cooling load is 60 kW with a sensible heat factor of 0.60, and the supply air temperature is 16 C db. At minimum load, about 7.5 kW with SHF of 0.80, the air quantity may be reduced no more than 75% by volume of the full load design value. Calculate the minimum volume of air to be supplied to the space at minimum load, cu.m/min.arrow_forward300 kg/min of water is required to be cooled from 50°C to 25°C in a wet cooling tower. For these purposes, 730 m3/min of atmospheric air is circulated through it at countercurrent. If the atmosphere is at a pressure of 94 kPa and the dry bulb and humid are 25°C and 15°C, respectively, and in the mixing process 3.7% of water is lost per evaporation, determine*:a) Relative and absolute humidity and dew temperature of the atmosphere.b) Absolute humidity and temperature of the air at the outlet.arrow_forwardProblem 2. Consider a Variable Air Volume (VAV) system, which serves for two rooms. The air temperature at the exist of the cooling coil is 10 °C. The design room temperature is 24 °C for both rooms. For room 1, the sensible and latent heat load is 60 and 10 kW, respectively. For room 2, the sensible and latent heat load is 40 and 10 kW, respectively. Determine (1) The mass flow rate for each room in kg/s; (2) The actual relative humidity of each room.arrow_forward
- * OMANTEL I. A moodle1.du.edu.om IVidi Keu out or 4.U P Flag question Air enters a 28-cm diameter pipe steadily at 200 kPa and 20°C with a velocity of 5 m/s. Air is heated as it flows, and leaves the pipe at 180 kPa and 40°C. The volume flow rate of air at the inlet (m3/s) is Select one: a. 0.608 O b. 0.408 O c. 0.508 d. 0.308 Droviouo nagn Noxt naanarrow_forward11arrow_forwardHow to solve theoretical efficiency of the cooling tower regarding air and water entering the system? Please provide examples. Subject : Heat transferarrow_forward
- b.) A variable-air-volume cooling system delivers air to a controlled space maintained at 24 C db and 17 C wb. Under design conditions, the total cooling load is 60 kW with a sensible heat factor of 0.60, and the supply air temperature is 16 C db. At minimum load, about 7.5 kW with SHF of 0.80, the air quantity may be reduced no more than 75% by volume of the full load design value. Determine the supply air conditions for minimum load (state dry bulb temperature and wet bulb temperature, both in degree C).arrow_forwardThe mass flow rate of the refrigerant in a Single Stage Vapor Compression (SSVC) refrigeration system is 0.015 kg/s and the evaporating and condensing temperatures shall be -20°C and 50°C, respectively. Determine the cooling capacity in tons.arrow_forwardQ3/ An auditorium is to be maintained at a temperature of 26°C dry bulb and 50% relative humidity. Air is to be supplied at a temperature not lower than 15°C dry bulb. The sensible heat gain is 110 kW and the latent heat gain is 37.5 kW. Take ventilating air as 25% by weight of the air from the room and is at 35°C dry bulb and 60% relative humidity. Determine the refrigeration capacity in tons of refrigeration (TR). Recirculated Air Auditorium 4 m. Conditioner 15°C m mo Qutside Air 3 Fan 26°C Cool Air 50%RH 35°C 60%RHarrow_forward
- The mass flow rate of the refrigerant in a Single Stage Vapor Compression (SSVC) refrigeration system is 0.015 kg/s and the evaporating and condensing temperatures shall be -20°C and 50°C, respectively. Determine the EER of the system.arrow_forwardA chilled water cooling coil receives 2.5 m3/s of air at 25 C db, 20 C wb. It is necessary for the air to leave the coil at 13 C db, 12 C wb. Assume sea level pressure. (a) Determine the SHF and the apparatus dew point. (b) Compute the bypass factor. (c) Compute the total and sensible heat transfer rates from the air using enthalpy difference and the SHF. (d) Compute the total and sensible heat transfer rates from the air using the bypass factor and the SHF.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
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