I want to cool Natural Gas from 195 Kelvin to 138 Klevin in a heat exchanger by using liquid nitrogen as the coolant medium. When entering the heat exchanger, the liquid nitrogen will have a pressure of 10 bar and temperature of 80 Kelvin. I need to find the necessary lenght of the heat exchanger. For this purpose i need to know the overall heat transfer coefficient of liquid nitrogen. I would be very glad if you could advise me where to find this value. I would also be glad if you could advise me other coolants in order to cool natural gas to 138 Kelvin.
Sorry but with overall heat transfer coefficient i ment convective heat transfer coefficient in W/m2K
See the attached document. I think, that for vertical tubes, the same authors have other similar document uploaded in Research Gate in July 2010.
Emilio Casado thank you very much Sir for your answer. I had another question...As I mentioned in my first question, i want to design a heat exchanger. The problem is that I dont know the mass flow rate of the liquid nitrogen. The only thing what known is that the natural gas must be cooled from 195 to 138 Kelvin. If i assume that the liquid nitrogen enters the heat exchanger with a temperature of 80Kelvin, how can i calculate the necessary lenght of the heat exchanger, without knowing the exit temperature and the mass flow rate of the nitrogen ?
You need also to know the flow rate of N2 to develop the design of the heat exchanger. First, calculate the heat to be exchanged with the flow rate of natural gas and their inlet and outlet temperatures. Second, with this heat, calculate the outlet temperature of the N2 in a similar form as before. Finally, calculate the overall heat transfer coeficcient, U, assuming a tube diameter and a number of tubes, taking into account the temperatures of both fluids. Calculate also the LMT (Logarithmic Medium Temperature) and with U, LMT and the transfered heat, calculate the required area of the heat exchanger. Changing the number of tubes and its diameter, repeat the proccessif you want a heat exchanger with other dimmensions.
Emilio Casado Thank you very much Sir. I had one last question. If i want to cool the gas in a heat exchanger by filling the device with dry ice, how could i determine the necessary tube lenght this time ? Since dry ice is solid, I thought that the heat transfer will be by conduction and tried to search for values for the thermal conductivity of the dry ice but couldnt find any. I would be very glad if you could help me also with this case.
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