what fluid can also be used in boiler other than water?
Mercury is being used as a fluid in the mercury boilers. A combined cycle is used to generate power from mercury boiler and the turbine exhaust of hot mercury vapors are used to generate steam that turns steam turbine to generate more power. You can surf mercury boilers on internet. Mercury is thermally efficient but not environmentally. So we need to do some research to find a liquid whose boiling point is less, thermal conductivity is high, specific heat is high, vapor density is high, vapor viscosity is low, corrosivity is low, combustibility is nil, toxicity is nil, cost to be low, degradation on high pressure and temperature to be low and it should sustain its physical and chemical properties through out the cycle.
whatever fluid you need to heat up.
Anything.... But economically water is the best and irreplaceable... If you use other fluid you need to design the whole heat cycle (all equipment including boiler) need to redesign according to that fluid properties...
There are many fluids that can be used, they usually need to have some very advantageous properties over water due to the expense of manufacture. But both the boiler and the equipment you are heating or powering from the boiler must be designed to use that fluid. Most of the readily available equipment has been designed to maximize the heat transfer properties of water. One non-water system is called an organic Rankine cycle, or ORC. It uses a lower boiling organic working fluid, like pentane or a refrigerant to transfer energy from a heat source by boiling in a vaporizer and using the vapor to turn a turbine generator. It is used in heat recovery systems and in geothermal applications.
Boilers are designed for water. I have not yet heard any boiler designed for fluid other than water. If you have this ordinary boiler, I recommend NOT to use it for any other liquid. If you intend to use boilers for other liquid, you need to consider some factors such as the following: - is your boiler supplying enough heat to boil your liquid (not too much to cause overheat, not too little not to bea able to boil the liquid), - compatibility of the fluid to boiler tubes (is it corrosive? specially at high temperatures?). - will it leave solid residue on the tubes when boiled? (not good for any boiler since it causes localized overheating on the tubes) In oil and gas industry, even water needs to be treated to be demineralized, de-aerated, etc.. to prevent corrosion and scale formation in the tubes so the boiler would somehow have a longer life.
