Thermodynamics: Vapor Compression Refrigeration that is Adiabatic?

[Sara1]

Consider a heat pump works on the vapor-compression refrigeration cycle with 0.2 kg/s of refrigerant-134a as the working fluid. The cycle is used to maintain a house at 26oC while absorbing heat from the outdoors at 3oC. R-134a enters the compressor at 200 kPa as a saturated vapor and leaves at 900 kPa, 50oC. The refrigerant leaves the condenser as a saturated liquid. Assuming the four devices to be well-insulated:

I need to find COP, but in order for that i need QH, which i can't have because all the devices are insulated. How do i proceed?

 

[RTW69]

COP (heating)=Q-hot/W-net,in

COP (heating)=M-dot * (h₂-h₄)/m-dot * (h₂-h₁)

Pt 1: 200 kPa,3 C
Pt 2: 900 KPa,50 C
Pt 4: 900 KPa, 26 C

See if that works

 

[RTW69]

Correction

Pt 1:200 kPa, sat. Vapor, -9 C

Pt 2: 900 kPa, 50 C

Pt 4: 900 kPa, sat. liquid, 35.4 C

Find enthalpy' s for various points, use equation for COP-heat

 

[Sara1]

Thank you

 

[DeeNos]

I would first clarify the question by asking for more information about the specific devices being referenced in the scenario. Are they well-insulated in a theoretical sense, or are they actually insulated in practice? If they are actually insulated, I would ask for more details about the insulation properties and whether any heat transfer occurs between the devices and their surroundings. This information would be necessary in order to accurately calculate the COP of the heat pump.

If the devices are truly well-insulated and no heat transfer occurs, then it is not possible to calculate the COP of the heat pump. This is because the COP is a measure of the heat transferred from the cold reservoir (outdoors) to the hot reservoir (inside the house) divided by the work done by the compressor. Without knowing the heat transfer, the COP cannot be determined.

In this case, I would suggest considering other factors such as the energy efficiency of the compressor and the environmental impact of using R-134a as the working fluid. Additionally, it may be helpful to explore alternative refrigeration cycles or technologies that could potentially improve the efficiency of the heat pump.