Journal
HEAT AND MASS TRANSFER
Volume 57, Issue 3, Pages 465-479Publisher
SPRINGER
DOI: 10.1007/s00231-020-02956-0
Keywords
Evaporation; Heat transfer; Pressure drop; Dimpled tube
Categories
Funding
- Research Chair Grant National Science and Technology Development Agency (NSTDA)
- King Mongkut's University of Technology Thonburi through the KMUTT 55th Anniversary Commemorative Fund
Ask authors/readers for more resources
The investigation found that the evaporative heat transfer coefficient of R-134a in dimpled tubes is significantly influenced by the dimpled depth, but less affected by the helical pitch and dimpled pitch. Experimental results provided a range for the heat transfer enhancement factor and pressure drop penalty factor, along with proposed correlations for predicting Nusselt number and friction factor during evaporation in dimpled tubes.
An investigation was experimentally performed to explore the influence of geometrical parameters on the evaporative heat transfer coefficient and pressure drop of R-134a in dimpled tubes. The test sections were the counter-flow tube-in-tube heat exchanger, where the refrigerant was evaporated in the inner tube and hot water flows in the annulus. Seven dimpled tubes with various helical pitches (p), dimpled pitches (z), and dimpled depths (e) were used as the test tubes. The test runs were carried out over mass fluxes of 300, 400, and 500 kg/m(2)s; heat fluxes of 20, 25, and 30 kW/m(2); and evaporating temperatures of 7, 10, and 13 degrees C. The results show the heat transfer enhancement factor (HF) and pressure drop penalty factor (PF) increase with a rise in e and a decrease in p and z. The HF and PF range between 1.03-1.7 and 1.76-9.00, respectively. The correlations for predicting the Nusselt number and the friction factor of R-134a during evaporation in dimpled tubes are proposed.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available