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Ambient Air - Temperature Ambient Convection Infiltration glass hA Effective Thermal Capacitance T C M Exfiltration Solar Automotive Climate Control Radiation Occupants Fres.. Air To = Tc+)(TH-TC) mo Inlet Heater Core SHARE ME Evaporator Blower Receiver Expansion Valve Accumulator Condenser Ambient Air Temperature Compressor Air Speed 1. Blend-door Temperature Control a) If the average air temperature leaving the evaporator and heater core are Tc' and TH', respectively, perform an energy analysis and show that the air temperature leaving the dash board registers, To', can be expressed as: b) If Tc' and TH' are 50 and 140F, respectively, plot the outlet temperature, To', as a function of mass flowrate ratio, , which can be controlled by blend-door position. 2. If during a hot summer day, a car having the following parameters: Ta' = 100F, U.A. = 1.25 Btu/minF, (hA) = 2.0 Btu/minF, Is allowed to sit in a parking lot without shade and reach steady-state, what will the air and internal mass temperatures reach with a solar load of 50 Btu/min? Ans: Ti 140F, T = 165F 3. If the same car as above was modified to be a hatch-back with a sun roof, and thus the solar load went up to 65 Btu/min, what would the initial temperatures become? Ans: T = 152F, T = 184.5F 4. Summer cool-down a) A car soaks in the hot sun for enough time to reach steady-state. Using the simplified model developed in class, predict the initial temperature, Ti', and the summer cool-down transient, T' T'(t), for 0 t5 min for the following parameters: To' = 50F Ta' = 100F Vo' = 250 ft/min Cv = 0.3 Btu/lbmF p', cp' = look up at appropriate temperature Make a graph of the above cool-down. b) Repeat the above but with four adult occupants (N=4), Q. = N(400) Btu/hr. c) What would the air flowrate, Vo', have to be increased to in order to have a similar performance to that with no occupants? Qs = 2500 Btu/hr M = 125 lbm Qo=0 U.A. = 50 Btu/hrF V' = 250 ft Note: Superimpose so that all three cool-down curves are on the same graph. Label carefully and completely, and clearly designate the three different curves. 5. Winter warm-up: a) A car sits outside all night. Use the model to predict for a cloudy day the winter warm-up transient, T' = T'(t), for 0 t 60 min for the following parameters: To' = 130F T' = 0F Qs = 0 Btu/hr Vo' = 250 ft/min M = 125 lbm cv = 0.3 Btu/lbmF p', cp' = look up at appropriate temperature b) Repeat the above for four occupants. Note: Label and plot both curves on one graph. Qo=0 U.A. = 50 Btu/hrF V' = 250 ft Ambient Air - Temperature Ambient Convection Infiltration glass hA Effective Thermal Capacitance T C M Exfiltration Solar Automotive Climate Control Radiation Occupants Fres.. Air To = Tc+)(TH-TC) mo Inlet Heater Core SHARE ME Evaporator Blower Receiver Expansion Valve Accumulator Condenser Ambient Air Temperature Compressor Air Speed 1. Blend-door Temperature Control a) If the average air temperature leaving the evaporator and heater core are Tc' and TH', respectively, perform an energy analysis and show that the air temperature leaving the dash board registers, To', can be expressed as: b) If Tc' and TH' are 50 and 140F, respectively, plot the outlet temperature, To', as a function of mass flowrate ratio, , which can be controlled by blend-door position. 2. If during a hot summer day, a car having the following parameters: Ta' = 100F, U.A. = 1.25 Btu/minF, (hA) = 2.0 Btu/minF, Is allowed to sit in a parking lot without shade and reach steady-state, what will the air and internal mass temperatures reach with a solar load of 50 Btu/min? Ans: Ti 140F, T = 165F 3. If the same car as above was modified to be a hatch-back with a sun roof, and thus the solar load went up to 65 Btu/min, what would the initial temperatures become? Ans: T = 152F, T = 184.5F 4. Summer cool-down a) A car soaks in the hot sun for enough time to reach steady-state. Using the simplified model developed in class, predict the initial temperature, Ti', and the summer cool-down transient, T' T'(t), for 0 t5 min for the following parameters: To' = 50F Ta' = 100F Vo' = 250 ft/min Cv = 0.3 Btu/lbmF p', cp' = look up at appropriate temperature Make a graph of the above cool-down. b) Repeat the above but with four adult occupants (N=4), Q. = N(400) Btu/hr. c) What would the air flowrate, Vo', have to be increased to in order to have a similar performance to that with no occupants? Qs = 2500 Btu/hr M = 125 lbm Qo=0 U.A. = 50 Btu/hrF V' = 250 ft Note: Superimpose so that all three cool-down curves are on the same graph. Label carefully and completely, and clearly designate the three different curves. 5. Winter warm-up: a) A car sits outside all night. Use the model to predict for a cloudy day the winter warm-up transient, T' = T'(t), for 0 t 60 min for the following parameters: To' = 130F T' = 0F Qs = 0 Btu/hr Vo' = 250 ft/min M = 125 lbm cv = 0.3 Btu/lbmF p', cp' = look up at appropriate temperature b) Repeat the above for four occupants. Note: Label and plot both curves on one graph. Qo=0 U.A. = 50 Btu/hrF V' = 250 ft
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Related Book For
Fundamentals of Thermal-Fluid Sciences
ISBN: 978-0078027680
5th edition
Authors: Yunus A. Cengel, Robert H. Turner, John M. Cimbala
Posted Date:
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