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
expand_more
expand_more
format_list_bulleted
Videos
Textbook Question
Chapter 3, Problem 3.53P
An interior zone of a large building is designed to have a supply air-flow rate of 5000 cfm (2.4 m3/s). The cooling load is constant at 10 tons (35 kW) with a SHF of 0.8 year-round. Indoor conditions are 75 F (24 C) db and 50 percent relative humidity (RH). (a) What is the maximum air dry bulb temperature and humidity ratio that would satisfy the load condition using all outdoor air? (b) Consider a different time when the outdoor air has a temperature of 40 F (4 C) db and 20 percent relative humidity. Return air and outdoor air may be mixed to cool the space. but humidification ill be required. Assume that saturated water vapor at 14.7 psia (101 kPa) is used to humidify the mixed air, and compute the amounts of outdoor and return air in cfm (m3/s). (c) At another time, outdoor air is at 65 F (18 C) db with a relative humidity of 90 percent. The cooling coil is estimated to have a minimum apparatus dew point of 45 F (7.2 C). What amount of outdoor and return air should be mixed before entering the coil to satisfy the given load condition? (d) What is the refrigeration load for the coil of part (c) above?
Expert Solution & Answer
Want to see the full answer?
Check out a sample textbook solution
Students have asked these similar questions
Q2) Air is supplied to an automobile cabin from the outside, where the temperature is 20F
and the relative humidity is 70%. It is desired to keep the cabin at 70F and Ø = 60%.
Hoe many pounds of water must be supplied to each pound of air entering the car
cabin if these conditions are to be met? The barometric pressure is 29.5 in.Hg.
%3D
Ans. (0.00797 lbs/Ibdry air)
ASHRAE standard 55, Thermal Environmental Conditions for Human Occupancy, notes
that for thermal comfort purposes, the indoor temperature should range from
approximately 67ºF to 82°F (19.4ºC to 27.8ºC), and systems designed to control humidity
must be able to maintain a dew-point temperature of 16.8°C (62.2°F).
ASHRAE standard 62.1, Ventilation and Acceptable Indoor Air Quality, recommends
that relative humidity in occupied spaces be controlled to less than 65% to reduce the
likelihood of conditions that can lead to microbial growth.
Determine the minimum allowable indoor temperature that will ensure a humidity control
system designed according to ASHRAE standard 55 will also satisfy the humidity
requirements of standard 62.1
In a place where a summer air-conditioning plant will be installed, 40% of the air entering the air-conditioning plant is the fresh air, and 60% is the return (bypass) air. The sensible heat gain of the place is 10 kW. and the latent heat gain is 2.5 kW.> Outdoor conditions: 32 °C DB, %50 RH.> Indoor conditions: 20 °C DB. %50 RH.> Take the relative humidity of the air passing through the cooling coil 90% at the coil outlet.
> The total air flow rate in the mixing chamber is 3000 m3/h> Take the density of the air as 1.2 kg/m3Based on the above.a) Show the process on a psychrometric diagram. b) Calculate the amount of fresh air. c) What is the value of enthalpy of blowing air. d) Calculate the ratio of by-pass air at cooling coil. e) Calculate the flow rate of by-passed air.
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...
Additional Engineering Textbook Solutions
Find more solutions based on key concepts
What parts are included in the vehicle chassis?
Automotive Technology: Principles, Diagnosis, and Service (5th Edition)
figure 4.44 shows a rectangular gate holding water behind it. If the water is 6.00 ft deep, compute the magnitu...
Applied Fluid Mechanics (7th Edition)
1.1 What is the difference between an atom and a molecule? A molecule and a crystal?
Manufacturing Engineering & Technology
Express force F as a Cartesian vector; then determine its coordinate direction angles. Prob. 2-87
INTERNATIONAL EDITION---Engineering Mechanics: Statics, 14th edition (SI unit)
The piston cylinder in Fig. P1.29 has a diameter of 4 in., inside pressure 100psia . What forcemust hold the ma...
Fundamentals Of Thermodynamics
27. A “normal” blood pressure has a gauge pressure of 120 millimeters of mercury [mm Hg] (systolic reading) ove...
Thinking Like an Engineer: An Active Learning Approach (4th Edition)
Knowledge Booster
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, mechanical-engineering and related others by exploring similar questions and additional content below.Similar questions
- In a place where a summer air-conditioning plant will be installed, 40% of the air entering the air-conditioning plant is the fresh air, and 60% is the return (bypass) air. The sensible heat gain of the place is 10 kW. and the latent heat gain is 2.5 kW.> Outdoor conditions: 32 °C DB, %50 RH.> Indoor conditions: 20 °C DB. %50 RH.> Take the relative humidity of the air passing through the cooling coil 90% at the coil outlet. > The total air flow rate in the mixing chamber is 3000 m3/h> Take the density of the air as 1.2 kg/m3Based on the above. Calculate the amount of fresh air. What is the value of enthalpy of blowing air. Calculate the ratio of by-pass air at cooling coil. Calculate the flow rate of by-passed air.arrow_forwardExample 1.12 Air at a dbt (dry bulb temprature) of 30 °C and a relative humidity of 30% is conveyed through a heated dryer where it is heated to a dbt of 80 °C. Then it is conveyed through a bed of granular pet food to dry it. The air exits the dryer at a dbt of 60 °C. The exit air is again heated to 80 °C and conveyed through another dryer containing another batch of pet food. The exit air from the second dryer leave at saturation. Clearly show the paths of air, starting from the ambient air to the saturated air exiting the second dryer on a copy of a psychrometric chart Determine the amount of water removed in the first and second dryer per kg of dry air.arrow_forwardQ.1 An air conditioning system supplying air to a space with a sensible heat load of 14 kW and a latent heat load of 9 kW has a cooling coil and a bypass path as shown schematically in Fig. The db- temperature of the space is maintained at 26°C. The dry air mass flow rate of supply air is 1.2kg/s. Outdoor ventilation air at 34°C db-temperature and 50% relative humidity is introduced into the system with a dry air mass flow rate of 0.26 kg/s. The air leaving the cooling coil is fully saturated at a db-temperature of 6°C. The pressure is constant at 101.3 kPa. Determine db-temperature and relative humidity of the supply air to the space, (ii) (i) (ii) (iv) wb-temperature of the space, temperature of the air entering the cooling coil, and refrigeration capacity of the cooling coil.arrow_forward
- Using a psychometric diagram, describe the heating and humidification process from the following data. Initially the air was at dry bulb temperature (DBT) 35 ° C and RH 35%. air preheated to DBT 85 ° C. The heated air is then flowed through a humidifier to increase the RH to 25%. for this process, count, a. change in absolute humidity of air from initial to final conditions = ..... (kg water / kg air) b. change in air enthalpy from initial to final conditions = ..... (kj / kg air)arrow_forwardAtmospheric air with an air flow rate of 200 liter/min and a dry bulb temperature of 35 °C and relative humidity of 40 % is cooled to 10 °C using an air conditioner. Determine: a) How much water per hour is removed from the air during the process; b) The cooling capacity of the air conditioner required to cool the air.arrow_forward2.) Moist air at 32∘Cdb and relative humidity of 60% enter a refrigeration system with a flow rate of 90 kg/min. Saturated air at 15∘Cdb leaves the system. Calculate: (a) the heat removed, in kW (b) moisture removed, in kg/sarrow_forward
- A sample of air is having dry bulb temperature 21°C and relative humidity 30% at barometric pressure of 760 mm of Hg. Find: 1. Partial pressure of vapor 2. Specific humidity 3. Wet bulb temperature and corresponding saturation pressure 4. Percentage humidity or degree of saturation 5. Specific volume of dry air 6. Dew point temperature 7. Enthalpy of moist air per kg of dry air Given: R - 0.287 kJ/kg K; cp dry air) = 1.005 kJ/kg K; specific heat of superheated vapor = 1.884 kJ/kg K and latent heat of vaporization at dew point temperature = 2493 kJ/kg. Do not use psychrometric chart. Psychrometric tables can be used.arrow_forwardMoist air at 32 degrees Cdb and relative humidity of 60% enter a refrigeration system with a flow rate of 90 kg/min. Saturated air at 15 degrees Cdb leaves the system. Calculate the heat and moisture removed in kW and kg/s respectively.arrow_forwardRH2 = 43% What is the specific humidity of the air stream #1, w1 (lbm H2O/lbm air)? What is the specific humidity of the air stream #2, w2 (lbm H2O/lbm air)? What is mass flow rate of dry air in stream #1 (lbm/s)? What is mass flow rate of dry air in stream #2 (lbm/s)? What is the relative humidity of the outlet (%)?arrow_forward
- What is the maxmium specific humidity of air at -30C is ________________and the maximum specific humdity of air at -10 C is _______________; therefore, the difference in maximum specific humidity between -30C and -10C is _____________. The maximum specific humidity of air at 30 C is ________________ and the maximum specific humidity of air at 10 C is ____________; therefore, the difference in maximum specific humidity between 30C and 10C is ______________.arrow_forwardASHRAE standard 62.2 states that the minimum acceptable rate of airflow into and out of a room is 15cfm (cubic feet per minute). If air is supplied at 68°F with a relative humidity of 45%, how many gallons of water (minimum) must be added to a portable room humidifier before you go to sleep if you would like to maintain the room at 65% humidity for 7 hours?arrow_forwardIn an air conditioning system, return air at 24°C dry-bulb temperature and 40% relative humidity is mixed with outdoor ambient air at 30°C dry-bulb temperature and 70% relative humidity. The dry air mass flow rate of outdoor air is 20% of the supply air mass flow rate to the space. The pressure is constant at 101.3 kPa.-Calculate the dry-bulb temperature of the supply air in °C.-The humidity ratio of the supply air.-The enthalpy of supply air in kJ/kg.arrow_forward
arrow_back_ios
SEE MORE QUESTIONS
arrow_forward_ios
Recommended textbooks for you
Elements Of ElectromagneticsMechanical EngineeringISBN:9780190698614Author:Sadiku, Matthew N. O.Publisher:Oxford University Press
Mechanics of Materials (10th Edition)Mechanical EngineeringISBN:9780134319650Author:Russell C. HibbelerPublisher:PEARSON
Thermodynamics: An Engineering ApproachMechanical EngineeringISBN:9781259822674Author:Yunus A. Cengel Dr., Michael A. BolesPublisher:McGraw-Hill Education
Control Systems EngineeringMechanical EngineeringISBN:9781118170519Author:Norman S. NisePublisher:WILEY
Mechanics of Materials (MindTap Course List)Mechanical EngineeringISBN:9781337093347Author:Barry J. Goodno, James M. GerePublisher:Cengage Learning
Engineering Mechanics: StaticsMechanical EngineeringISBN:9781118807330Author:James L. Meriam, L. G. Kraige, J. N. BoltonPublisher:WILEY
Elements Of Electromagnetics
Mechanical Engineering
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Oxford University Press
Mechanics of Materials (10th Edition)
Mechanical Engineering
ISBN:9780134319650
Author:Russell C. Hibbeler
Publisher:PEARSON
Thermodynamics: An Engineering Approach
Mechanical Engineering
ISBN:9781259822674
Author:Yunus A. Cengel Dr., Michael A. Boles
Publisher:McGraw-Hill Education
Control Systems Engineering
Mechanical Engineering
ISBN:9781118170519
Author:Norman S. Nise
Publisher:WILEY
Mechanics of Materials (MindTap Course List)
Mechanical Engineering
ISBN:9781337093347
Author:Barry J. Goodno, James M. Gere
Publisher:Cengage Learning
Engineering Mechanics: Statics
Mechanical Engineering
ISBN:9781118807330
Author:James L. Meriam, L. G. Kraige, J. N. Bolton
Publisher:WILEY
The Refrigeration Cycle Explained - The Four Major Components; Author: HVAC Know It All;https://www.youtube.com/watch?v=zfciSvOZDUY;License: Standard YouTube License, CC-BY