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Flow boiling heat transfer at low flux conditions in a domestic refrigerator evaporator
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.ORCID iD: 0000-0002-9902-2087
2008 (English)In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 31, no 6, 1021-1032 p.Article in journal (Refereed) Published
Abstract [en]

This paper investigates the flow boiling heat transfer in a typical domestic refrigerator evaporator with horizontal flow, frequent bends and a non-circular cross-section. The mass flux was varied between 21 and 43 kg/m(2) s, the heat flux between 1 and 5 kW/m(2) and the vapour quality between 0.2 and 0.8. In spite of a predicted stratified to wavy-stratified flow pattern complete tube perimeter wetting was believed to occur except for the lowest mass flux and for positions upstream of the first bend. it was concluded that the bends helped wetting the tube perimeter. The experimental data revealed heat transfer coefficients higher than predicted with conventional correlations. This was suggested to be explained by thin film evaporation at a perimeter repeatedly wetted by liquid slugs. A simple correlation based on the pure convective part of the Shah correlation [3] was derived from the experimental data. The mean deviation of this was 16.9% compared to Shah's 54.7%.

Place, publisher, year, edition, pages
2008. Vol. 31, no 6, 1021-1032 p.
Keyword [en]
domestic refrigerator, survey, experiment, heat transfer, boiling, isobutane, parameter, speed, flow, horizontal tubes, pattern
URN: urn:nbn:se:kth:diva-17873DOI: 10.1016/j.ijrefrig.2007.12.017ISI: 000259847400010ScopusID: 2-s2.0-48649088704OAI: diva2:335918
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2012-04-11Bibliographically approved
In thesis
1. Energy Efficiency Improvements in Household Refrigeration Cooling Systems
Open this publication in new window or tab >>Energy Efficiency Improvements in Household Refrigeration Cooling Systems
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is based on eight articles all related to the characteristics of the cooling system and plate evaporator of a household refrigerator. Through these articles, knowledge is provided that can be used to increase the operational efficiency in household refrigeration. Papers A, B and C focus on heat transfer and pressure drop in a commonly used free convection evaporator – the plate evaporator. Applicable correlations are suggested on how to estimate the air side heat transfer, the refrigerant side pressure drop and the refrigerant side heat transfer. Papers D, E and F hold a unique experimental study of the refrigerant charge distribution in the cooling system at transient and steady state conditions. From this cyclic losses are identified and estimated and ways to overcome them are suggested. In paper G the topic “charging and throttling” is investigated in an unparalleled experimental study based on more than 600 data points at different quantities of charge and expansions device capacities. It results in recommendations on how to optimize the capillary tube length and the quantity of refrigerant charge. Finally, Paper H holds a thermographic study of the overall cooling system operating at transient conditions. Overall, a potential to lower the energy use by as much as 25 % was identified in the refrigerator studied. About 10 % was found on the evaporator’s air side. 1-2 % was identified as losses related to the edge effect of the evaporator plate. About 8 % was estimated to be cyclic losses. About 5 % was found in cycle length optimization.  It is believed that most of these findings are of general interest for the whole field of household refrigeration even though the results come from one type of refrigerator. Suggestions of simple means to reduce the losses without increasing the unit price are provided within the thesis

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 115 p.
TRITA-REFR, ISSN 1102-0245 ; 12:02
Household refrigerator, Domestic refrigerator, Free convection, Plate evaporator, Heat transfer, Flow boiling, Isobutane, R600a, Pressure drop, Two-phase, Cooling system, Charge inventory, Cyclic losses, Thermography
National Category
Energy Engineering
urn:nbn:se:kth:diva-93061 (URN)978-91-7501-306-0 (ISBN)
Public defence
2012-04-27, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)

QC 20120411

Available from: 2012-04-11 Created: 2012-04-10 Last updated: 2014-02-11Bibliographically approved

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Björk, Erik T.Palm, Björn E.
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