SushmaLokapur

I may get heat of around 30-35 degree celsius. I wanted to know, can I use that heat in culturing Duckweeds? If not, can somebody please suggest some other systems in which this heat can be utilized.?

30 - 35 deg C is ambient temperature in the shade in many places. It is not clear from where you harvest such a near ambient heat. It almost seems to be a non starter.
Why duckweed? It is a stagnant water plant , which may one day be a source of protein. Some claim it as a water cleanser. If uncontrolled, it can become a pest like water hyacinth. I do not know if 30 -35 C is required for this plant or how you can deliver this heat to a large body of water.
You may get better response from readers if you make a detailed post of where you are recovering the heat from.

bioramani

30 - 35 deg C is ambient temperature in the shade in many places. It is not clear from where you harvest such a near ambient heat. It almost seems to be a non starter.
Why duckweed? It is a stagnant water plant , which may one day be a source of protein. Some claim it as a water cleanser. If uncontrolled, it can become a pest like water hyacinth. I do not know if 30 -35 C is required for this plant or how you can deliver this heat to a large body of water.
You may get better response from readers if you make a detailed post of where you are recovering the heat from.

I was thinking about recovering the heat from the side walls of refrigerator or from the walls of conventional boilers (which we use in home) and using that heat in some useful purpose. I can even increase the temperature upto 50 degree or so if i work on it,i think (may be by increasing the area of heat transfer or using the material of better thermal conductivity).

Second law will not allow that. I doubt if you get to even 40C with those sources. The cost of collection and reuse will also be much more than the recovered energy. It is not clear how this heat will be delivered for use. Again the second law will get into the act. If you use water or air as the heat sink, you will need a pump or blower to move the heat to point of use.

Better look at other options.

bioramani

Second law will not allow that. I doubt if you get to even 40C with those sources. The cost of collection and reuse will also be much more than the recovered energy. It is not clear how this heat will be delivered for use. Again the second law will get into the act. If you use water or air as the heat sink, you will need a pump or blower to move the heat to point of use.

Better look at other options.

Thanks a lot, sir. I'll think over it and consider your suggestion.. 😀