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Measurement of film thickness and temperature on horizontal thermal spray coated tube falling film evaporator using interferometric technique.

Number: 2392

Author(s) : MALIACKAL A. K., GANESAN A. R., MANI A.

Summary

'Water' is the 'Essence of Life'. It is an irreplaceable precious resource that is core of life on earth, a vital commodity that is critical for human survival, socio-economic developments and for the preservation of a healthy ecosystem. Current trends indicate that two-thirds of the world's population will be living in water- stressed countries by 2025(wat (2006)). In order to eradicate or to provide su_cient water requirement for mankind desalination plays a pivotal role. This paper presents studies on horizontal tube falling _lm evaporator for Multi e_ect desalination (MED) system with spray coated tubes. The most important component in any MED system is the falling _lm evaporator. The wide acceptance for this kind of evaporators is because of the fact that it is character- ized by a very low-pressure drop. In MED systems, falling _lm evaporation takes place outside the tube geometry utilizing the latent heat of condensing vapour inside the tube. Convective evaporation, as well as low-temperature nucleate boiling, occur in the _lm as it ows over the tube depending on the operating conditions(Abraham and Mani (2015)). The liquid falls on the top of the tube and ows down along the curved tube surface. There is a phase change on both sides of the tube and the evaporation outside the tube helps vapour to be separated from the liquid as soon as it is formed. Two di_erent tubes surfaces were studied, namely bare copper tube and copper tube coated with alloy of Al2O3 and TiO2. Scanning electron microscope, Energy-dispersive X-ray spectroscopy, 3D surface pro- _lometer were utilized to study about the surface texture, composition and to _nd surface roughness values attributed with each tubes. An optical shadow method (non-intrusive) incorporating Otsus's algorithm was used to evaluate the _lm thickness around the circumference of the cylinder, and a Mach-Zehnder Interferometer (MZI) was employed to visualize the isotherm formation (Maliackal et al. (2021)). All studies were performed for complete wetting of the tube. The measured _lm thickness was compared with commonly used empirical formulas. Further, the e_ectiveness of using those empirical formulas for small diameter tubes was analyzed. A novel interferometric technique was used to analyze the _lm interface temperature, and a comparative study was performed for the two di_erent tube geometries. A standard error of mean (SEM) analysis was performed on every data set.

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Pages: 13

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Details

  • Original title: Measurement of film thickness and temperature on horizontal thermal spray coated tube falling film evaporator using interferometric technique.
  • Record ID : 30028471
  • Languages: English
  • Subject: Technology
  • Source: 2021 Purdue Conferences. 18th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2021/05
  • Document available for consultation in the library of the IIR headquarters only.

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