Pressure Calculation in Closed Loop PV Thermal

[skaboy607]

Hi

I am trying to design a closed loop testing system for a solar thermal system using water as the heat transfer medium. There a number of fittings and and pipework involved, the water might reach temperatures up to 80/90 deg C.

I am trying to calculate what the max pressure in the system might be so I can apply a safety factor and spec the components out from there. I'm pretty sure I could do this if the medium was air using the ideal gas law for various states but with water, this falls down and I am kind of at a loss.

I can't even really say that the process is constant volume because there is a pump in the loop so work will be done.

I might be missing something here or making it to complicated but would appreciate some guidance.

Thanks in advance

 

[Achy47]

Hello,

Thank you for your question. Designing a closed loop testing system for a solar thermal system can be a challenging task, but with the right approach, it can be done successfully.

First, let's start by understanding the basics of the system. In a closed loop system, the volume of the fluid (in this case, water) remains constant, so the ideal gas law cannot be applied. However, the liquid will expand when heated, and this expansion will create pressure in the system.

To calculate the maximum pressure in the system, you will need to consider several factors, such as the volume of the system, the temperature of the water, the type and size of the fittings and pipework, and the flow rate of the pump. You may also need to take into account any potential pressure drops due to friction in the pipework.

One way to approach this problem is to use the Bernoulli's equation, which relates the pressure, velocity, and elevation of a fluid in a closed system. This equation can help you determine the pressure at different points in the system and provide an estimate of the maximum pressure.

Another approach is to use a simulation software specifically designed for thermal systems, which can help you model and analyze the behavior of the system under different conditions. This will provide more accurate results and take into account all the variables involved.

In any case, it is essential to apply a safety factor to your calculations to ensure the system can handle any unexpected pressure spikes or fluctuations. This will help you select the right components and ensure the safety of the system and its users.

I hope this helps guide you in the right direction. If you need further assistance, please don't hesitate to reach out. Good luck with your project!