Calculation of the discharge volume of thermal expansion safety valves
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In the calculations for thermal expansion safety valves, regarding the value of heat input, how should this heat be calculated for safety valves installed on pipes heated by hot water? What conditions need to be known?
I have a question: For example, if the heating temperature for the process pipe is maintained at 20 degrees, the discharge temperature of the safety valve is 25 degrees, the ambient temperature is -14 degrees, the pipe length is 50 meters, and the pipe diameter is 6 inches, do I just need to calculate the amount of heat absorbed by the liquid inside those 50 meters of pipe as it heats from 20 degrees to 25 degrees? That amount of heat would then be the heat required for the expansion of the safety valve. But how do I calculate the heat for this section of pipe? Using the formula Q = W*CP*(t2-t1), the liquid in this pipe isn’t in motion, so I can’t use flow rates to calculate anything; thus, a time factor is missing – specifically, the time it takes for the temperature to rise from 20 degrees to 25 degrees； If we calculate based on the heat provided by the heat tracing tube, the heat amount calculated using standard heat tracing methods assumes a flowing state. I assume that by using hot water to maintain a temperature of 25 degrees, it is also possible to calculate a certain amount of heat – is this amount of heat sufficient for the safety valve to discharge?
Can the safety valve still release pressure if the medium is flowing?
The problem now is the condition of no fluid flow – how to determine the heat generated