The system i have is a bio-chemical reaction generating 5Kw of heat,but the operating temperature is just 42C(My room temperature is 35C).I want to use minimum pump and fan power.Currently i am using radiators and heat exchangers but couldn solve the issue.
Appears you will need forced air, and lots of surface area on the radiators and heat exchangers. You can measure the surface temperature of the radiators you have and get an idea of whether or not they will be efficient with forced air. .
Try some evaporative cooling.
