1. The problem statement, all variables and given/known data I need to know how much the temperature drops after an inline heater which heats an airflow of 5 lbs/min up to 88 °C with an pressure of 54 PSI. When the air exits the heater it is released into the free air where it is 20 °C. I know that the air will expand to a bigger volume then, which will lead to a temperature drop. So I need to know how much this drop will be. 2. Relevant equations P1 * V1^γ=P2 * V2^γ T1 * V1^(γ-1)=T2 * V2^(γ-1) 3. The attempt at a solution γ= 1.4 V1= 5 lbs = 1.853 m3 T1= 88 °C = 361 K P1= 54 PSI = 3723163.9 P2= 101325 Pa V2= ? T2= ? P1 * V1^γ=P2 * V2^γ V2 = 4.69447 m3 T1 * V1^(γ-1)=T2 * V2^(γ-1) T2 = 248 K This will say that the temperature decreases to -25 °C which sounds like a wrong answer in my opinion. I also thought to use the ideal gas law with --> P*V= m*Rs*T But I dont know how I should use it in my case.. Anybody who can give me a solution?