A heat pump has a work input of 2 kW and provides 7 kW of net heat transfer to heat a house. The system is steady, and there are no other work or heat interactions. Is this a violation of the first law of thermodynamics? Select one: a. Yes b. No

Question

Kaylah Anderson

Engineering

27 October, 17:19

A heat pump has a work input of 2 kW and provides 7 kW of net heat transfer to heat a house. The system is steady, and there are no other work or heat interactions. Is this a violation of the first law of thermodynamics? Select one: a. Yes b. No

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Answers (1)

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Nina Carlson · Answer 1

No, is not a violation of the first law of thermodynamics.

Explanation:

The first law of thermodynamics states that energy is neither created nor destroyed in an isolated system (a system without mass or energy transfer with ambient).

In a heat pump work is used to transfer heat from a cold body to a hot body (see figure). In a free system heat would go from the heat source to the cold one, that is why you need work. Work and heat are energy in transit.

W + Qin = Qout

In your case

2 kW + Qin = 7 kW

Qin = 5 kW

It would be a violation to the first law of thermodynamics if Qout is less than 2 kW.