It was the purpose of this investigation to formulate design information about the heat transfer process in a refrigerant condenser tube when the flow velocity and the fluid quality are high. Under these conditions the condensate spreads out around the tube circumference to form an annular liquid film. This liquid film was shown to constitute a major portion of the thermal resistance for heat leaving a tube. For example, a 0.01 in. thick layer of liquid Rl2 inside a 1/2 in. diameter tube will constitute 96% of the total thermal resistance. The condensate thickness depends on the velocities of the liquid and vapor phases, the quality, the temperature difference across the film, etc.
The heat transfer was studied experimentally on the inside of a horizontal 3/8 in. ID glass tube and a 9/32 in. ID aluminum tube, each 50.5 in. long. Heat transfer coefficients were measured between 60 Btu/hr ft² deg F and 700 Btu/hr ft² deg F while the temperature difference between the bulk Rl2 and the inside tube surface varied from 4 F to 40 deg F. Fluid quality was studied over a range from 0.60 to 0.98 and the total mass flow rate ranged from 70 lb/hr to 300 lb/hr.
A modified integral technique was formulated from the experimental results. This analysis provides a practlcai method for calculating the local and average heat transfer coefficient and the condensate layer thickness along the tube.
Citation: ASHRAE Transactions, Volume 77, Part 1, Philadelphia, PA
Product Details
- Published:
- 1971
- Number of Pages:
- 8
- File Size:
- 1 file , 710 KB
- Product Code(s):
- D-PH-2187
