Question

(6. (20 points) A heat pump is to be used to heat a house in winter and then reversed to cool the house in summer. The interior space is to be maintained at 20°C. Heat transfer through walls and roof is estimated to be x=0.525 kJ/sec per degree difference in temperature between inside and outside. (6a) (Sp) In winter if the outside temperature is 5°C, what is the minimum power required to drive the heat pump? (6b) (12p) For the same power requirement, in summer what is the maximum outside temperature for which the reversed heat pump (air conditioner) can maintain an inside temperature of 20°C.

A heat pump is to be used to heat a house in winter and then reversed to cool the house in summer. The interior space is to be maintained at 20oC. Heat transfer through walls and roof is estimated to be χ = 0.525 kJ/sec per degree difference in temperature between inside and outside. (6a) (8p) In winter if the outside temperature is 5oC, what is the minimum power required to drive the heat pump? (6b) (12p) For the same power requirement, in summer what is the maximum outside temperature for which the reversed heat pump (air conditioner) can maintain an inside temperature of 20oC.

Answer 1

(6a) Given, 5C Outside temperture o2Ks (aT) Rate heat leaktnq into om 2oc =OS25 (2o-s) 7-8S w (нр W 20t 273 .OP - 19. 533 20-5) Desfred effed . 333 work frpu oKinput 19-33 Here the desired effect is to eliminate the heat eakna into room. T be the maximem outside temperature. let o.525(T-20) 24 3 C.o1 O40) T-2D (T-20) 2 27 36 0.525(AT) T 3S.07°c