Session: Research Posters

Paper Number: 119876

119876 - Experimental Assessment of Heat Transfer During Condensation of R32 Over Single Horizontal Plain, 2d and 3d Integral Finned Tubes 

The demand for energy conservation and environmental concerns requires improvement and upgrades in the refrigeration and air-conditioning sectors. Various regulations and protocols have been adopted to combat environmental pollution, such as the Montreal Protocol, the Kigali Amendment, and European F-gas regulations. Those regulations lead the refrigeration and air-conditioning sectors to look for refrigerants with low GWP and zero ODP. Because of its availability, performance, and efficiency, R32 is a popular choice. R32 offers more capability as a straight system replacement. As a result, a redesigned R32 system can use smaller displacement compressors to accomplish the same capacity.

The film-wise condensation heat transfer method applies in different engineering areas, such as industrial and household-level refrigeration and air conditioning devices, chemical processing industries, and marine propulsion. It is the most promising and desirable mode of heat transfer due to its higher heat transfer coefficient when compared to other ways of heat transfer.

For the past few decades, various scholars have extensively made theoretical and experimental assessments to study and augment the condensation heat transfer performance over single and bundle tube surfaces. The application of fins over the tube surface and various surface structural configurations are among those improvement techniques. Further, these improvements helped to keep the shell and tube-type condensers compact and efficient.

The advancements in manufacturing technology can help with the flexible development of three-dimensional fin profiles from the optimum two-dimensional finned tubes. However, condenser tubes with various three-dimensional surfaces, which exhibit superior enhancement factors in single condenser tests, have a stronger bundle effect in the full-set condenser than the common two-dimensional integrally finned tubes. The continuous fins of low-fin tubes may operate as dams to avoid the axial diffusion of film condensate, which would explain the favorable row effect.

This paper has experimentally assessed the enhancement in the condensing side heat transfer coefficient of R32 over the single horizontal plain, 2D, and 3D enhanced integral finned tubes. An experimental setup has been constructed, and a separate investigation has been conducted over the plain tube to check the experimental integrity and for comparison purposes. The Nusselt’s correlation predicted 80% of the experimental results of the plain tube, with an error band ranging from 0-10%. Then an experimental investigation was conducted over the 2D integral fin tube, followed by the fully and partially spined 3D enhanced integral finned tubes. The 2D integral finned tube fin density has been chosen to be 32 FPI, the best-performing fin density specifically for the refrigerant R32, which has been experimentally reported in our recently published article. The three 3D spined integral finned tubes have been manufactured by making axial slots using the best-performing 2D integral finned tube. The impacts of various core parameters, such as subcooling temperature and heat flux, have been assessed on the performance parameters of condensing side heat transfer coefficient and heat transfer enhancement ratio. The experimental assessments have been conducted at a condensing vapor temperature of 40 °C and a subcooling temperature ranging from 3-11 °C. The experimental findings have been correlated with other related works in the literature. For the condensation of R32, the spine integral finned tubes outperformed the 2D integral finned tubes by around 23%. Compared to the 2D integral finned tubes, the partially spine integral finned tubes (only the bottom side) showed an increment in the heat transfer coefficient ranging from 11-20%. The condensation of R32 over the top spine integral finned tube revealed an insignificant enhancement factor (only 1.4%) compared to the 2D integral finned tube. The highest average heat transfer enhancement factor of 6.4 has been recorded for the fully spined 3D integral finned tube. At the same time, the lowest average heat transfer enhancement factor was recorded, 5.7, by the 2D integral finned tube. The experimental results have been compared with the theoretical models of the Honda Nozu and Kumar Models; the Honda Nozu Model revealed minimum under-prediction with an average deviation percentage of 20%.

Presenting Author: Ibrahim Mustefa Mohammed Indian Institute of Technology Roorkee

Presenting Author Biography: Ibrahim Mustefa Mohammed received a B.Sc. degree in Mechanical Engineering from Bahir Dar University, Ethiopia, in 2010, and an MTech. degree in mechanical engineering from the National Institute of Technology, Warangal, India, in 2014. He is currently a Ph.D. candidate in the Mechanical and Industrial Engineering department at the Indian Institute of Technology, Roorkee, India. His area of research is an experimental Investigation on the enhancement of film-condensation over 2D and 3D low-finned integral tubes using the retrofit refrigerant R32. He has been working on his research, out of which he has gained three research articles. His research interests include Heat Transfer, Automobile Engineering, Computational Fluid Dynamics, and Energy Technologies.

Authors:

Ibrahim Mustefa Mohammed Indian Institute of Technology Roorkee
Ravi Kumar Indian Institute of Technology Roorkee