Question

I am designing a gas heater and a heat exchanger for a swimming pool. As I am starting with my calculations for the heat exchanger, one of the values that I do not have is the exit temp of the water that enters the swimming pool after the water is heated in the heat exchanger. I know that I need to do a control volume equation to work this out, but I do not know where to go from there. I know that the swimming pool will have some losses like: loss of heat by conduction to the surface that surrounds the pool, loss of heat by evaporation of the water, losses by convection on the free surface of the water. Also just to give more clarity regarding the concept: water will be pumped out of the swimming, sent through a filter, sent through a heat exchanger, and sent back to the swimming pool, what flow rate of water, at what temp, will increase the temp of the swimming pool in a period of time?

Answer 1

The first thing that will need to be fixed is the flow rate of water. Basically, in this case, the flow rate will depend on the pump flow output.

Once the flow output is determined by you(according to your pump output flow), the can be attained by using the equation cp = Heat input per sec;

where = mass flow rate of water from pump(from flow rate of pump)

  cp= specific heat of water(standard value: 4.186 J/gram⁰C)

= Temp. rise of water(to be calculated)

Depending on the amount of heat generated upon heating "x" amount of fuel per sec. The heat input can be calculated as

Heat input per sec= x* calorific value of fuel.

Depending on amount of fuel burnt in one hour can give the temp rise of water in a given specific time.