2nd law of thermodynamics heat pump problem

In summary, the conversation discusses an inventor's claim of developing a heat pump with a 180 kW heating effect and consuming 70 kW of power while using a heat source at 273 K. The question is whether this claim is possible, and the suggested equations to determine the validity of the claim are COP and thermal efficiency. The conversation ends by asking for the definition of COP and mentioning an example in Cengel CH 6.
  • #1
hazzz
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Homework Statement


Here is the problem:

An inventor claims to have developed a heat pump that provides a 180 kW heating effect for a
293 K household while only consuming 70 kW of power and using a heat source at 273 K. Can this
claim be possible?

Homework Equations


COP of heat pump = Qh/W
COP of heat pump (carnot max) = Th/(Th-Tl)
n (thermal efficiency) = W/Qh = 1-(Ql/Qh)
n(max carnot) = 1- (Tl/Th)

The Attempt at a Solution


The answer to this problem is that the claim is valid because the COP of the heat pump is less than the COP max, I just want to know can I use thermal efficiency instead of COP to see if this claim is valid?
 
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  • #2
Well, what is the definition of the COP ?
Cengel CH 6 has plenty examples (check 6-78)
 

FAQ: 2nd law of thermodynamics heat pump problem

1. What is the 2nd law of thermodynamics and how does it apply to heat pump problems?

The 2nd law of thermodynamics states that in any energy conversion process, the total entropy (measure of disorder) of the universe will always increase. In the case of heat pump problems, this means that the heat transfer from a colder source to a hotter sink requires an input of external work, as it goes against the natural direction of heat flow.

2. How does a heat pump work according to the 2nd law of thermodynamics?

A heat pump works by using external work to transfer heat from a colder source to a hotter sink. This is possible because the 2nd law of thermodynamics allows for the conversion of work into heat, but not the reverse. Therefore, a heat pump can move heat from a colder source to a hotter sink, but not the other way around without an input of external work.

3. Can a heat pump violate the 2nd law of thermodynamics?

No, a heat pump cannot violate the 2nd law of thermodynamics. The law states that the total entropy of the universe must always increase, and a heat pump only transfers heat from a colder source to a hotter sink by using external work. This means that the overall entropy of the universe is still increasing, as the work input is contributing to the increase in entropy.

4. How does the 2nd law of thermodynamics impact the efficiency of a heat pump?

The 2nd law of thermodynamics dictates that no energy conversion process can be 100% efficient. This means that a heat pump can never transfer all the heat from a colder source to a hotter sink, and some work input will always be lost as waste heat. The efficiency of a heat pump is therefore limited by the 2nd law of thermodynamics.

5. What are some real-world applications of the 2nd law of thermodynamics in heat pump problems?

The 2nd law of thermodynamics has important applications in various heat pump systems, such as refrigerators, air conditioners, and geothermal heat pumps. It also plays a crucial role in energy production and conversion processes, such as power plants and engines. Understanding the 2nd law of thermodynamics is essential for designing and improving these systems for maximum efficiency.

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