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Energy Efficiency Improvements in Household Refrigeration Cooling Systems
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
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.
Series
TRITA-REFR, ISSN 1102-0245 ; 12:02
Keyword [en]
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
Identifiers
URN: urn:nbn:se:kth:diva-93061ISBN: 978-91-7501-306-0 (print)OAI: oai:DiVA.org:kth-93061DiVA: diva2:514733
Public defence
2012-04-27, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20120411

Available from: 2012-04-11 Created: 2012-04-10 Last updated: 2014-02-11Bibliographically approved
List of papers
1. Air Side Heat Transfer of a Domestic Refrigerator Plate-Type Evaporator
Open this publication in new window or tab >>Air Side Heat Transfer of a Domestic Refrigerator Plate-Type Evaporator
2003 (English)Conference paper, Published paper (Other academic)
Place, publisher, year, edition, pages
Valencia, Spain: Academic Conferences Publishing, 2003
Series
Eurotherm Seminar No 72, Thermodynamics, Heat and Mass Transfer of Refrigeration Machines and Heat Pumps
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-78945 (URN)
Conference
The Eurothern Seminar
Available from: 2012-02-08 Created: 2012-02-08 Last updated: 2012-04-11Bibliographically approved
2. Flow boiling heat transfer at low flux conditions in a domestic refrigerator evaporator
Open this publication in new window or tab >>Flow boiling heat transfer at low flux conditions in a domestic refrigerator evaporator
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%.

Keyword
domestic refrigerator, survey, experiment, heat transfer, boiling, isobutane, parameter, speed, flow, horizontal tubes, pattern
Identifiers
urn:nbn:se:kth:diva-17873 (URN)10.1016/j.ijrefrig.2007.12.017 (DOI)000259847400010 ()2-s2.0-48649088704 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
3. PRESSURE DROP IN A PLATE EVAPORATOR FOR REFRIGERATORS
Open this publication in new window or tab >>PRESSURE DROP IN A PLATE EVAPORATOR FOR REFRIGERATORS
2002 (English)Conference paper, Published paper (Refereed)
Abstract [en]

This study examines the two-phase refrigerant side pressure drop in a plate evaporator used in a refrigerator. The refrigerant was Isobutane (R600a). The refrigerant channel had a non-circular cross-section best described as a circular segment. It was found that the best estimation of the frictional pressure drop was with a homogeneous method and with a modified version of the separated Lockhart and Martinelli method.

Keyword
refrigerator, pressure drop, evaporator, isobutane, R600a
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-93053 (URN)
Conference
HEFAT2002
Note
QC 20120411Available from: 2012-04-10 Created: 2012-04-10 Last updated: 2012-04-11Bibliographically approved
4. A simple technique for refrigerant mass measurement
Open this publication in new window or tab >>A simple technique for refrigerant mass measurement
2005 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 25, no 8-9, 1115-1125 p.Article in journal (Refereed) Published
Abstract [en]

A simple technique for refrigerant mass measurement is described and evaluated. First, quick-closing valves trap the refrigerant in the section under consideration. Then, the refrigerant is expanded into a tank, thus reaching a superheated state. Finally the mass is calculated by p-nu-T relationship. The technique was implemented on a domestic refrigerator and was computer automated (no need for manual intervention). Preliminary (1) data are reported of the charge distribution during an on-off cycle.

Keyword
charge inventory, void fraction, domestic refrigerator
Identifiers
urn:nbn:se:kth:diva-14587 (URN)10.1016/j.applthermaleng.2004.09.008 (DOI)000227503300002 ()2-s2.0-13444274600 (Scopus ID)
Note

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-05-03Bibliographically approved
5. Refrigerant mass charge distribution in a domestic refrigerator. Part I: Transient conditions
Open this publication in new window or tab >>Refrigerant mass charge distribution in a domestic refrigerator. Part I: Transient conditions
2006 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 26, no 8-9, 829-837 p.Article in journal (Refereed) Published
Abstract [en]

Experimental results are presented of the refrigerant mass charge distribution in a steadily cycling domestic refrigerator. In detail it is shown how the charge is displaced at compressor start-up and shut-down. At start-Lip it was found that the charge was temporarily displaced towards the condenser before returning to a steady state distribution in the latter part of the on-period. As a result, initially the evaporator was starved with a lowered evaporation temperature and a peak 10 degrees C superheat. The superheat disappeared within 3 min as the evaporator was gradually refilled with refrigerant. At shut-down the pressure equalised within 3 min as refrigerant was pushed into the evaporator from the condenser. The losses due to charge displacements were estimated to 11% (capacity) and 9% (efficiency). Possible ways to reduce the losses are discussed.

Keyword
domestic refrigerator, charge inventory, capillary tube, dynamic simulation, cycling losses, system, freezer
Identifiers
urn:nbn:se:kth:diva-15551 (URN)10.1016/j.applthermaleng.2005.10.003 (DOI)000236308200007 ()2-s2.0-29244464681 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
6. Refrigerant mass charge distribution in a domestic refrigerator. Part II: Steady state conditions
Open this publication in new window or tab >>Refrigerant mass charge distribution in a domestic refrigerator. Part II: Steady state conditions
2006 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 26, no 8-9, 866-871 p.Article in journal (Refereed) Published
Abstract [en]

Experimental results are presented of the refrigerant mass charge distribution in a steady state operating domestic refrigerator at varied thermal loads. It was found that the charge decreased in the evaporator and increased in the condenser and compressor upon increased thermal load. No subcooling or superheat was observed over the range of capacities tested (74-145 W). The combination of a low side accumulator and an expansion device with high capacity (short capillary tube) explained this. The study suggests that a capillary tube throttled cooling system, with a floating condensation temperature, can handle large load variations without becoming destabilised (superheat or subcooling) just like a more sophisticated thermostatic expansion device control system.

Keyword
domestic refrigerator, charge inventory, capillary tube, capillary-tube flow, dynamic simulation, cycling losses, freezer, model
Identifiers
urn:nbn:se:kth:diva-15552 (URN)10.1016/j.applthermaleng.2005.10.004 (DOI)000236308200012 ()2-s2.0-29244461751 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
7. Performance of a domestic refrigerator under influence of varied expansion device capacity, refrigerant charge and ambient temperature
Open this publication in new window or tab >>Performance of a domestic refrigerator under influence of varied expansion device capacity, refrigerant charge and ambient temperature
2006 (English)In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 29, no 5, 789-798 p.Article in journal (Refereed) Published
Abstract [en]

This paper reports experimental results of an on/off cycling domestic refrigerator at varied expansion device capacity (EDC), quantity of charge and ambient temperature. It was found that the energy consumption is insensitive to varied EDC and charge within a wide range of settings. For the charge this is explained by the low side accumulator, which buffers over- and undercharge. It was also found that the optimum charge increased at lower ambient temperature. The paper describes an experimental procedure on how to determine the capillary tube length and the quantity of charge for a domestic refrigerator/freezer. This procedure is recommended since it takes different thermal masses and loads into consideration and since the potential for energy saving with a more sophisticated method appears to be limited.

Keyword
domestic refrigerator, experiment, performance, parameter, thermostatic expansion device, refrigerant charge, temperature, capillary-tube flow, mass charge, dynamic simulation, cycling losses, part ii, model, freezer
Identifiers
urn:nbn:se:kth:diva-15825 (URN)10.1016/j.ijrefrig.2005.11.008 (DOI)000238810800012 ()2-s2.0-33744939982 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
8. A thermographic study of the on-off behavior of an all-refrigerator
Open this publication in new window or tab >>A thermographic study of the on-off behavior of an all-refrigerator
2010 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 30, no 14-15, 1974-1984 p.Article in journal (Refereed) Published
Abstract [en]

In this work a thermographic camera is used to observe the temperature distribution of a household refrigerator cooling system operating at on off cycling conditions. This technique offers an alternative method to analyze the cooling system compared to conventional thermocouples. In particular it is interesting to view the overall picture of how the refrigerant charge is distributed over the cooling system at transient conditions. In addition, four sources of energy losses were identified and discussed. Out of these losses, two would have been difficult to find using conventional thermocouple temperature measurements. (C) 2010 Elsevier Ltd. All rights reserved.

Keyword
Household refrigerator, Thermography, Hear exchanger, Cooling system
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-26858 (URN)10.1016/j.applthermaleng.2010.04.032 (DOI)000280892400010 ()2-s2.0-77955468943 (Scopus ID)
Note
QC 20101201Available from: 2010-12-01 Created: 2010-11-29 Last updated: 2017-12-12Bibliographically approved

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Citation style
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  • modern-language-association-8th-edition
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  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
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  • Other locale
More languages
Output format
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