Question

A) Describe the operation of a heat pump operating on the theoretical reversed Carnot cycle, with a neat sketch of the layout.

Answer 1

Answer:

a) The operation of a heat pump involves the extraction of energy in the form of heat Q₁ from a cold source

b) The modifications required to convert a plant operating on an ideal Carnot cycle to a plant operating on a Rankine cycle involves

i) Complete condensation of the vapor at the condenser to saturated liquid for pumping to the boiler

ii) Heating of the pumped, pressurized water to the boiler pressure

Explanation:

a) 1 - 2. Wet vapor enters compressor where it undergoes isentropic compression to state 2 by work W₁₂  

2 - 3. The vapor enters the condenser at state 2 where it undergoes isobaric and isothermal condensation to a liquid with the evolution of heat  Q₂

3 - 4. The condensed liquid is expanded isentropically with the work done equal to W₃₋₄

4 - 1. At the state 4, with reduced pressure from the previous expansion, the liquid makes its way to the evaporator where it absorbs heat, Q₁, from the body to be cooled.

b. i) Complete condensation of the vapor at the condenser to saturated liquid for pumping to the boiler

Here the condensation process is modified from partial condensation to complete condensation at the same temperature which reduces the size of the pump required to pump the liquid water as opposed to pumping steam plus liquid

ii) Heating of the pumped, pressurized water to the boiler pressure

The pumped water at state 4 will be required to be heated to saturated water temperature equivalent to the boiler pressure, hence heat will need to be added at state.

Sketches of the schematic of a Basic Rankine cycle is attached