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International Journal of Refrigeration
IPC Science and Technology Press
International Journal of Refrigeration

IPC Science and Technology Press

0140-7007

International Journal of Refrigeration/Journal International Journal of RefrigerationSCIEI
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    Application of heuristic algorithms for design optimization of industrial heat pump

    Oh B.S.Cho J.Choi B.Lee G....
    15页
    查看更多>>摘要：The design parameters of heat pumps are related to each other nonlinearly or in a complicated manner; therefore, it is difficult to determine the optimal combination of design parameters, such as superheat, subcooling, and refrigerant type, analytically. To address this limitation, three representative heuristic algorithms, namely the genetic algorithm (GA), particle swarm optimization (PSO), and simulated annealing (SA), are applied to optimize a heat pump under the given process conditions. Heuristic algorithms are driven based on randomness; thus, the consistency of the calculation results and computational time represent the decision criteria for the appropriate optimizer. The GA is unsuitable as a heat pump optimizer because it requires an excessive number of iterations. In contrast, PSO and SA have a similar capability of consistency and calculation time with a rational number of iterations. In conclusion, PSO exhibits a slightly better consistency and use of computational resources; therefore, PSO is selected as the heat pump design optimization algorithm in this study. The novelty of this work lies in that the related design parameters of the heat pump are simultaneously globally optimized with minimal physical background, and the heuristic algorithm that is most applicable to heat pump design optimization is determined.
      原文链接:
    • NSTL
    • Elsevier

    Effect of tip geometry on the performance of low-speed axial flow fan

    Moosania M.ZHOU C.HU S.
    8页
    查看更多>>摘要：Low-speed axial flow fans are widely used especially in air conditioning and ventilation systems. The performance of axial flow fans is negatively affected by the blockage and loss resulted from the tip leakage vortex (TLV) and the reverse flow. This paper investigates the development of TLV in a partially shrouded fan used in the outdoor unit of an air-conditioning system. It was found that the TLV follows the blade tip chord, due to the radial inflow in the initial unshrouded part of the blade, unlike the fully covered fan. Thus, the TLV trajectory can be manipulated by modifying the blade tip chord shape. It was also found that the reverse flow from the outlet near the shroud is driven by the negative component of TLV. The blade tip chord was modified to be in the axial direction before reaching the shrouded part to reduce the blockage and negative component of TLV. Comparing the results for the modified blade shows that the reverse flow and TLV blockage are effectively reduced by adjusting the TLV trajectory to be along the fan's rotational axis. The maximum flow rate increased up to 12% accompanied by a noticeable reduction in the loss by the tip modification.
      原文链接:
    • NSTL
    • Elsevier

    An inverse fault detection and diagnosis (IFDD) strategy for practical application on chiller product

    Lu H.Cui X.Han H.Zhang Y....
    11页
    查看更多>>摘要：Current research on chiller fault detection and diagnosis (FDD) is usually based on the multi-classification method for mixed multiple fault types. The establishment of a multi-classification FDD model requires obtaining extensive test data of normal operation and multiple common faults at different fault levels, so the cost-to-benefit ratio will not be accepted. In addition, because of the information interference between different types of fault data, FDD model is hard to avoid over-fitting or under-fitting, and there may be an intolerable high false alarm rate existing in product application. Therefore, it is difficult to promote FDD in actual chiller product applications. This paper proposes an inverse fault detection and diagnosis (IFDD) strategy, which is based on the characteristics of the target fault (the fault to be concerned) to establish a two-classification fault diagnosis model. Compared with the multi-classification method, the amount of fault test data required by the two-classification methods to realize fault diagnosis can be greatly reduced. With IFDD strategy, the detection and diagnosis are completed simultaneously, while fast calculation speed, high diagnosis accuracy rate and low false alarm rate are achieved. The core of the IFDD strategy is to concentrate resources to capture the characteristics of the target fault, and no longer classify other types of faults and normal operating conditions, so it can avoid the influence of information interference between multiple types of fault data in the fault diagnosis model. In order to verify the feasibility of this strategy, a 200 ton variable-speed screw chiller has been tested on the laboratory, and a database of normal operation, refrigerant leakage, refrigerant overcharge faults, and a new operating condition of insufficient cooling water flow is initially established. Based on the sensors configured by the chiller unit and using the exponentially weighted moving-average (EWMA) control chart for IFDD, the model's fault diagnosis accuracy for the target fault reaches 100%, and no false alarm appears after the transition period.
      原文链接:
    • NSTL
    • Elsevier

    Computational fluid dynamics analysis of flammable refrigerant leakage through a microcrack

    Zhang S.Chen G.Li Z.Fang J....
    10页
    查看更多>>摘要：Hydrofluorocarbons(HFCs) are potent greenhouse gases in refrigeration systems, and their contribution will accelerate climate change. In the context of global warming, low global warming refrigerants have to be reconsidered, these refrigerants are commonly flammable, so systems that use them can pose a risk. Thus, an analysis of potential pipe leaks in refrigeration systems is urgently needed. In existing research on refrigerant leak, most studies have examined holes as leak points. However, the true morphology of leak points is commonly long and extremely narrow. Therefore, a round-pipe microcrack leak model with crack opening displacement (COD) ranging from 10 to 50 μm were built to perform a simulation and experiment. The Fluent (v.20, ANSYS Inc.) software performed computational fluid dynamics analysis. The R290, R32, and R1234yf refrigerants were simulated, and the orifice flow equation was introduced to calculate leakage from the microcrack. An axial and circumferential microcrack model was constructed, and the experiment validated the simulation with largest relative error of 2.9%. The simulation results indicated that for side flow through the microcrack, using the conventional discharge coefficient (Cd) in the orifice equation may be unsuitable. Accordingly, based on the simulation results, empirical equations for predicting the Cd of axial microcrack when R290, R32, and R1234yf are leaking are obtained. Additionally, the effect of length-to-diameter ratio and orifice-to-pipe-diameter ratio on Cd are also discussed. Compared with existing studies, a smaller infinity discharge coefficient value (Cd∞) was observed when COD < 30 μm.
      原文链接:
    • NSTL
    • Elsevier

    Falling film evaporation experiment and data processing method of R1234ze (E) on horizontal enhanced tubes

    Ouyang X.-P.Sun K.
    10页
    查看更多>>摘要：For two kinds of specially made enhanced tubes with outer diameters of 19 and 25 mm, the falling film evaporation experiment was carried out by using environmental refrigerant R1234ze (E) under the experimental condition that the water velocity in the tube was controlled from 1 to 3.5 ms?1. "The Wilson-Gnielinski Separation Method" and "The Wilson-Gnielinski-Heat Flux Correction Method" were used to process the experimental data. The comparative analysis showed that when the heat fluxes of all the test points outside the tube were constant, the results of two calculation methods were almost the same. When the heat fluxes of all the test points outside the tube were fluctuant, the results of two calculation methods were different and the heat flux correction method should be applied to reduce the error. The enhanced tube with outer diameter of 19 mm was used to investigate the heat transfer performance of falling film evaporation, with spray density ranging from 0.03 to 0.1 kgm?1 s?1, heat flux ranging from 15 to 45 kWm?2 and evaporation temperature ranging from 0 to 25 °C. And the enhancement rate inside the tube was obtained by using the heat flux correction method. Finally, the variation trends of the overall heat transfer coefficient and the outside tube heat transfer coefficient under different working conditions were both obtained experimentally and analyzed theoretically.
      原文链接:
    • NSTL
    • Elsevier

    Flammability inhibition effects of R227ea, R125, R134a, and R744 on 3,3,3-trifluoropropene (R1243zf)

    Wu X.Zhang X.Tang F.Xu S....
    9页
    查看更多>>摘要：3,3,3-trifluoropropene (R1243zf or HFO-1243zf) has low global warming potential, which is expected to be an excellent alternative to hydrofluorocarbon refrigerants in air conditioning and refrigeration systems, but its flammability hinders the practical applications. This paper reports the experimental results of the flammability inhibition effects of carbon dioxide (R744), 1,1,1,2,3,3,3-heptafluoropropane (R227ea), pentafluoroethane (R125), and 1,1,1,2-tetrafluoroethane (R134a) on R1243zf. The measured critical suppression ratios decrease in the order: R744 (3.1) > R134a (1.42) >R125 (0.68)> R227ea (0.58), which are also predicted by group contribution method. The flammability limit range of R1243zf was estimated as per three methods, and the closest estimation values to tested data was obtained by using the Jones’ method (the stoichiometric concentration for combustion method). Finally, the mechanisms of flammability inhibition effect differences of R744, R227ea, R125, and R134a on R1243zf were analyzed, from the views of the combustibles or oxidants dilution, combustibles and oxidants isolation, and/or free radical production and consumption. A hydrofluorocarbon flame retardant that has the big F/H ratio and produces much free radical CF3 during its thermal decomposition, exhibits the good flammability inhibition efficiency to R1243zf.
      原文链接:
    • NSTL
    • Elsevier

    Experimental study of ammonia flow boiling in a vertical tube bundle: Part 3 – Enhanced dimple tube with 2/3rd height solid round PVC nonconductive rod

    Ayub Z.Ayub A.Abbas A.Ismail T....
    10页
    查看更多>>摘要：This paper presents the experimental results of saturated two-phase flow ammonia in a vertical shell and tube heat exchanger comprising of seven dimpled enhanced tubes with solid PVC nonconductive round rods inserted in the lower 2/3rd section of each tube creating 67% annular section. The source of heat was hot ethylene glycol/water solution flowing on the shell side. The range of saturation temperature for ammonia was -20 °C ≤ Tsat ≤ -2 °C, heat flux range 5 kW m?2 ≤ q˙ ≤ 45 kW m?2, exit vapor quality range 0.1 ≤ x ≤ 0.9 and mass flux 76.9 kg m?2 s?1≤ G ≤ 145.7 kg m?2 s?1. For each saturation temperature, the effects of heat flux and mass flux were studied while the exit vapor quality at each mass flux varied between 0.1 and 0.9. Around 40% increase in heat transfer performance was observed with saturation temperature between –20 and –2 °C at exit vapor quality of 0.7. Heat transfer performance also increased with heat flux at fixed mass flux at each saturation temperature while the performance showed initial increase with quality and then a drop at the onset of dry out.
      原文链接:
    • NSTL
    • Elsevier

    Numerically investigated on the transient performance of fast cool-down J-T cryocoolers with non-isometric structure

    Wei C.Chen H.Liu Y.
    12页
    查看更多>>摘要：To achieve fast cool-down is important for the miniature Joule-Thomson (J-T) cryocooler in infrared detectors and other applications. A novel non-isometric helically coiled heat exchanger, with a first-sparse-then-dense type structure, was adopted in this study to improve the cool-down performance of miniature J-T cryocoolers. A transient model that takes real gas characteristics, heat leakage and compressible flow into account, was established and verified. The transient thermodynamic behaviors (temperature, internal heat load, mass flow rate and cooling capacity) of J-T cryocoolers with the typical, first-dense-then-sparse and first-sparse-then-dense type structure were analyzed and compared to obtain the better performance. It can be concluded that the first-sparse-then-dense structure can increase the cool-down rate by 13.4% with a smaller structural mass. Besides, different operating conditions with charging pressure and cylinder capacity were also simulated and analyzed. The results show that the first-sparse-then-dense structure always has the fastest cool-down rate in any operating condition. The simulation results can be used for the accurate prediction of system performance and structural design.
      原文链接:
    • NSTL
    • Elsevier

    A3 and A2 refrigerants: Border determination and hunt for A2 low-GWP blends

    Calleja-Anta D.Nebot-Andres L.Cabello R.Sanchez D....
    9页
    查看更多>>摘要：The hunt for new refrigerant blends has been concentrated to locate A1 refrigerants. However, the investigation for A2 or A2L blends to replace hydrocarbons (A3) has not attracted attention yet, although these mixtures will allow to increase the maximum charge of refrigeration systems from 500 g to 1200 g. This paper extends Linteris’ et al. work to define, for first time, the frontier between A3 and A2 ASHRAE safety classifications with an approach that can avoid large experimental campaigns. Then, using the methodology, it determines the composition limits of possible A2 binary blends with hydrocarbons that have a GWP below 150. Only mixtures of hydrocarbons with A2 or A2L components meet the criteria, and the composition of the least flammable fluid is predominant. Proposed hypothesis, developed theoretically, should be completed in the future with experimentation, to quantify the energy performance of found blends.
      原文链接:
    • NSTL
    • Elsevier

    Experimental study of an oil-free swing vane compressor

    Heng K.R.Ooi K.T.Chan W.K.
    10页
    查看更多>>摘要：Conventional compressors must always be operated in the upright orientation to ensure that the oil sump is always located at the lowest position to allow the collection of lubricant back to the oil sump by gravity. As a result, conventional compressors are not suitable for applications where orientation-free and portability of the system are required. Applications such as wearable cryogenic cooling bags for the ease of vaccine transportation, compact cryogenic coolers for space applications or even as a portable oxygen concentrator (POC) for ambulatory patients will not be feasible with current compressors. A direct solution would be to eliminate the need for oil lubrication in the operation of a compressor. This would require a successful development of an oil-free compressor. In this work, an oil-free swing vane compressor prototype was designed, instrumented and tested. Its performance was evaluated with air and R134a as working fluids. For experiments with air at 1080 to 1800 rev min?1, pressure ratios of up to 4.08 with mechanical and volumetric efficiencies ranging from 22.0% to 40.0% and 30.9% to 67.5% were obtained, respectively. For experiment with R134a at 1620 rev min?1, the prototype has achieved mechanical and volumetric efficiencies of 45.1% and 55.5%, respectively, with a coefficient of performance (COP) of 1.25. Potential failure modes of this oil-free compressor have been identified and recommendations for design improvement are also presented in this study.
      原文链接:
    • NSTL
    • Elsevier