Question

A thermoelectric refrigeration unit is used to dehumidify a plant growth chamber on the International Space Station. The device draws 120 watts. Its coefficient of performance varies according to the temperature gap ∆T = T_H – T_C and can be modeled as:

COP = 9 – 0.48∆T +.006 (∆T)².

where T_C is the chamber setpoint temperature and T_H is the temperature outside the growth chamber. Experience shows that essentially all heat removed by the unit is latent heat from condensation of water vapor inside the chamber (plants transpire lots of water as they grow)

a) When the chamber is at 25°C and temperature outside it is 35°C, how much water vapor can be condensed per hour by the thermoelectric unit?

b) If a Carnot refrigerator could be substituted for the thermoelectric unit in part (a), how much power would it require to condense water at the same rate?

c) Find the isentropic efficiency of the thermoelectric cooling system – that is, the ratio of the COP of the real system to the COP of the ideal Carnot system. Don’t be surprised if it’s terrible. Thermoelectrics aren’t very efficient but they are lightweight, silent, and (since they have no moving parts) ultra-reliable and maintenance free - all good qualities for spacefaring equipment.

Answer 1

Solution → Te 25"c = 235 k cop # g-o.us (AT) t o.o 6 (AT) were. ΔΤ> TH-Tc 3o5-298 Now 120 hoans @ Cof Wilf Wlip Wi リ(Amor 다26-Xloc [4.45 %