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  • 1.
    Björk, Erik
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Energy Efficiency Improvements in Household Refrigeration Cooling Systems2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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

  • 2.
    Björk, Erik
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    PRESSURE DROP IN A PLATE EVAPORATOR FOR REFRIGERATORS2002Konferensbidrag (Refereegranskat)
    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.

  • 3.
    Björk, Erik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Acuña, José
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Granryd, Eric
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Mogensen, Palne
    Nowacki, Jan-Erik
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Palm, Björn
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Weber, Kenneth
    Bergvärme på djupet: Boken för dig som vill veta mer om bergvärmepumpar2013 (uppl. 100)Bok (Övrig (populärvetenskap, debatt, mm))
    Abstract [sv]

    I den här boken får du lära dig mer om bergvärmepumpar. Hur fungerar en värmepump? Hur gör man en lönsamhetskalkyl? Hur upphandlar man? Kan man trimma sitt system? Dessutom: lär dig mer om radiatorsystemet, berget och kollektorn.

  • 4.
    Björk, Erik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Palm, Björn
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Nordenberg, Johan
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    A thermographic study of the on-off behavior of an all-refrigerator2010Ingår i: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 30, nr 14-15, s. 1974-1984Artikel i tidskrift (Refereegranskat)
    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.

  • 5.
    Björk, Erik T.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    A simple technique for refrigerant mass measurement2005Ingår i: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 25, nr 8-9, s. 1115-1125Artikel i tidskrift (Refereegranskat)
    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.

  • 6.
    Björk, Erik T.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Palm, Björn E.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Flow boiling heat transfer at low flux conditions in a domestic refrigerator evaporator2008Ingår i: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 31, nr 6, s. 1021-1032Artikel i tidskrift (Refereegranskat)
    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%.

  • 7.
    Björk, Erik T.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Palm, Björn E.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Performance of a domestic refrigerator under influence of varied expansion device capacity, refrigerant charge and ambient temperature2006Ingår i: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 29, nr 5, s. 789-798Artikel i tidskrift (Refereegranskat)
    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.

  • 8.
    Björk, Erik T.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Palm, Björn E.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Refrigerant mass charge distribution in a domestic refrigerator. Part I: Transient conditions2006Ingår i: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 26, nr 8-9, s. 829-837Artikel i tidskrift (Refereegranskat)
    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.

  • 9.
    Björk, Erik T.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Palm, Björn E.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Refrigerant mass charge distribution in a domestic refrigerator. Part II: Steady state conditions2006Ingår i: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 26, nr 8-9, s. 866-871Artikel i tidskrift (Refereegranskat)
    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.

  • 10.
    Björk, Erik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Tjahyo Setiawan, Arrie
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Palm, Björn
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik.
    Air Side Heat Transfer of a Domestic Refrigerator Plate-Type Evaporator2003Konferensbidrag (Övrigt vetenskapligt)
1 - 10 av 10
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