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Kupiaine Kerttu - One of the best experts on this subject based on the ideXlab platform.

  • R134a kylmäaineen höyrystyminen Plate and Shell -lämmönsiirrin järjestelmissä
    2017
    Co-Authors: Kupiaine Kerttu
    Abstract:

    The liquid chillers are refrigeration systems that remove heat from a secondary refrigerant. The secondary refrigerant, such as water, is then distributed to the location where refrigeration is needed. The main components of chiller are a compressor, an expansion valve and two heat exchangers: the evaporator and the condenser. The scope of this thesis was to research the chiller systems and the evaporation of the refrigerant 134a in the flooded Plate and shell evaporator. The Plate and shell heat exchanger consist of a Plate Pack inside a shell. The experimental research focuses on the effect of the Plate surface roughness. The Plates of the Plate Pack were roughened with glass ball blasting in terms of increased heat transfer. The tests were carried out with the R134a chiller plant and the thermosiphon system: first, using a standard Plate Pack and then, treated Plate Pack. No significant improvements in heat transfer coefficient were observed. However, the significant effect of the oil was noticed in the R134a chiller tests. The thermosiphon test was carried out with pure refrigerant (R134a and NH3) and, as a result, muchhigher heat transfer coefficients were achieved. The present technology of the chiller is concentrated on R134a, but it may be assumed that a shift towards natural refrigerants can take a place in near future. In the future research, more attention shall be focused on the applications used with natural refrigerants as well as the oil behaviour. The roughened Plate surface does not prove to be beneficial in the heat transfer, thus, the research shall target on Plate macro structure or pattern, to further improve the heat transfer

Raj M Manglik - One of the best experts on this subject based on the ideXlab platform.

  • experimental study of turbulent flow heat transfer and pressure drop in a Plate heat exchanger with chevron Plates
    Journal of Heat Transfer-transactions of The Asme, 1999
    Co-Authors: Arun Muley, Raj M Manglik
    Abstract:

    Experimental heat transfer and isothermal pressure drop data for single-phase water flows in a Plate heat exchanger (PHE) with chevron Plates are presented. In a single-pass U-type counterflow PHE, three different chevron Plate arrangements are considered: two symmetric Plate arrangements with {beta} = 30 deg/30 deg and 60 deg/60 deg, and one mixed-Plate arrangement with {beta} = 30 deg/60 deg. For water (2 < Pr < 6) flow rates in the 600 < Re < 10{sup 4} regime, data for Nu and f are presented. The results show significant effects of both the chevron angle {beta} and surface area enlargement factor {phi}. As {beta} increases, and compared to a flat-Plate Pack, up to two to five times higher Nu are obtained; the concomitant f, however, are 13 to 44 times higher. Increasing {phi} also has a similar, though smaller effect. Based on experimental data for Re {ge} 1000 and 30 deg {le} {beta} {le} 60 deg, predictive correlations of the form Nu = C{sub 1}({beta}) D{sub 1}({phi}) Re{sup p1({beta})} Pr{sup 1/3} ({mu}/{mu}{sub w}){sup 0.14} and f = C{sub 2}({beta}) D{sub 2}({phi}) Re{sup p2({beta})} are devised. Finally, at constant pumping power, and depending upon Re, {beta}, and {phi}, the heat transfermore » is found to be enhanced by up to 2.8 times that in an equivalent flat-Plate channel.« less

Arun Muley - One of the best experts on this subject based on the ideXlab platform.

  • experimental study of turbulent flow heat transfer and pressure drop in a Plate heat exchanger with chevron Plates
    Journal of Heat Transfer-transactions of The Asme, 1999
    Co-Authors: Arun Muley, Raj M Manglik
    Abstract:

    Experimental heat transfer and isothermal pressure drop data for single-phase water flows in a Plate heat exchanger (PHE) with chevron Plates are presented. In a single-pass U-type counterflow PHE, three different chevron Plate arrangements are considered: two symmetric Plate arrangements with {beta} = 30 deg/30 deg and 60 deg/60 deg, and one mixed-Plate arrangement with {beta} = 30 deg/60 deg. For water (2 < Pr < 6) flow rates in the 600 < Re < 10{sup 4} regime, data for Nu and f are presented. The results show significant effects of both the chevron angle {beta} and surface area enlargement factor {phi}. As {beta} increases, and compared to a flat-Plate Pack, up to two to five times higher Nu are obtained; the concomitant f, however, are 13 to 44 times higher. Increasing {phi} also has a similar, though smaller effect. Based on experimental data for Re {ge} 1000 and 30 deg {le} {beta} {le} 60 deg, predictive correlations of the form Nu = C{sub 1}({beta}) D{sub 1}({phi}) Re{sup p1({beta})} Pr{sup 1/3} ({mu}/{mu}{sub w}){sup 0.14} and f = C{sub 2}({beta}) D{sub 2}({phi}) Re{sup p2({beta})} are devised. Finally, at constant pumping power, and depending upon Re, {beta}, and {phi}, the heat transfermore » is found to be enhanced by up to 2.8 times that in an equivalent flat-Plate channel.« less