Thermodynamic principles of capture and re-use of heat of POC:
Capture and re-use of heat of POC must be integrated. A heat exchanger integrates capture and reuse of heat. In the heat exchanger hot fluid (POC) flows co-current or counter-current to cold fluid, say air. Both fluids are separated by a wall. Hot fluid enters the heat exchanger at temperature  and exits at temperature  .
Wall is heated by the heat transferred from the hot POC. Cold fluid enters the heat exchanger at temperature  and leaves at  such that  .
Heat balance over an infinitesimally small element of length dx can be written at steady state
| Heat lost by hot fluid = Heat gained by the cold fluid − Heat loss from the element to the surrounding |
(1) |
Let  and mc are mass of hot fluid and cold fluid, CPh and CPc are the specific heat of hot and cold fluid then we can write
 |
(2) |
In eq.2, dTh and dTc are the change in temperatures of hot and cold fluid at any position along the length of the exchanger.
in an ideal adiabatic-reversible heat exchange between hot and cold fluid, dQ = zero and the process is reversible when temperature difference between hot and cold fluid at any position along the length of the heat exchanger,
i.e. provided
|
