最新刊期
卷 35 ， 期 3 ， 2014
- 摘要：Refrigeration mal-distribution in a distributor located at the inlet of a heater exchanger plays an important role in the heat exchanger performance. This paper proposes a test method to measure the mass flow rate and quality of each branch tube after distributor. Three types of distributors (pressure drop; centrifugal and reservoir) were manufactured and tested. It was found that with the increase of mass flow rate, the performance of distributor improved. The pressure drop and centrifugal type is more sensitive than reservoir one. With the increase of inlet quality, the performance of distribution deteriorates. The flow behavior of two-phase refrigerant such as phase distribution and separation phenomena was studied by CFD, which helped investigate how the geometry factors influence the distribution performance.关键词：distributor;two-phase;distribution uniformity;CFD1971|2002|0发布时间：2024-07-18
- 摘要：The safety and stability of the refrigerating systems onboard have a great effect on the application of refrigerator driven by waste heat from fishing vessels and the natural cooling system used in nuclear powered vessels, which infers the importance of studying the performance of heat transfer and flow at ocean conditions. This study gives a brief review of the influence of ship vibration and rolling motions at sea on the performance of heat and mass transfer in fluid-filled tanks and refrigerating systems. Investigations on great amount researches indicate that effect of vibration and rolling motions on heat and mass transfer and flow characteristics depends on the level of vibration and rolling. The absorption refrigeration system can be easily affected at ocean conditions except during mild vibrations while researchers also found that by adding baffles or porous medium to the liquid tank can effectively improve the stability of fluid-filled tanks.关键词：ship;vibration;rolling;heat transfer;absorption;fluid-filled tank1904|1936|0发布时间：2024-07-18
- 摘要：Ice storage is a promising technology for energy saving. Ice slurry is favorable material for ice storage. To overcome the shortcomings of the present method of ice slurry production, a new ice storage system is developed to produce ice slurry with low humidity. It drives a liquid desiccant cycle to obtain an environment of low water vapor pressure. Droplets keep on evaporating in such an environment and become super-cooled. Then the super-cooled state will be released with a releaser to get ice slurry in the same way of the conventional super-cooled water method. The system mainly consists of two important processes, liquid dehumidification and evaporative super-cooling. These two processes were investigated by experiments. The results prove the feasibility of the new system and expose some method for future optimization. Meanwhile, Ice was formed in the experiments, which shows a good potential of the system.关键词：ice storage;ice slurry;liquid dehumidification;evaporation1918|1977|0发布时间：2024-07-18
- 摘要：The heat transfer performance of evaporator and condenser is the key factor which has an effect of the power efficiency on the refrigeration and power generation units. An experimental investigation of evaporator and condenser heat transfer with different inlet and outlet hot water temperature was conducted. The cycle working fluid was R245fa. The experiment showed that the evaporator heat transfer coefficient decreased and condenser heat transfer coefficient increased first and then decreased with increasing inlet hot water temperature. The higher heat water temperature, the higher evaporation pressure; Evaporator heat transfer coefficient can reach to 2500 W/(m2?℃).关键词：R245fa;evaporator;condenser;heat transfer performance;mid-low temperature resource;waste heat utilization1794|1940|0发布时间：2024-07-18
- 摘要：In the ground source heat pump (GSHP) system, the temperature around the borehole heat exchangers (BHEs) would continue to spread further with running time, in addition the groundwater flow would have an important impact on the thermal dispersion. Based on the heat transfer model considering groundwater flow in aquifers, the approximate analytical expression of temperature plume distance was obtained, the factors including groundwater flow velocity，subsurface thermal conductivity and porosity affecting on the temperature plume distance were analyzed by comparing with infinite line source (ILS) model. The results from test platform showed that the temperature plume distance under the groundwater flow velocity was greatly larger than the distance under the pure conductive model and it was different along the axial direction of BHE. In the zone with the groundwater velocity larger than 1×10-6m/s, the distance of 8-10m between the boreholes was recommended for design along the groundwater flow direction.关键词：groundwater flow;borehole exchanger;temperature plume distance1799|1935|0发布时间：2024-07-18
- 摘要：This paper studied the effect of oil circulation rate on the performance of reciprocating refrigeration compressor by means of experiments. In order to ensure the experiment accuracy, double oil separators were adopted in the testing system. In this way, the refrigerant was almost separated completely from the mixture of refrigerant and oil and entered again into the suction of the compressor. A model of Sanyo compressor was used to carry out a series of experiments. The results showed that the oil circulation rate was increased with the increase of the amount of oil injection, the oil circulation rate effected the refrigerant capacity, power, COP and discharge temperature. The performance of compressor and discharge temperature was increased with the lower oil circulation rate and vice versa. Therefore, the proper quantity of oil should be injected into the compressor, where a good lubrication condition was formed, the reliability and performance of compressor were guaranteed and a better economy can be obtained.关键词：oil;refrigeration compressor;oil circulation rate;performance2017|1960|0发布时间：2024-07-18
- 摘要：Ice crystal formation is one of the factors that causes cell damage during crvopreservation process．Ice crystal will provide fundamental information for the development of appropriate cryopreservation protocols．Effects of concentration and properties of solutions for the growth and shape of ice crystals were studied by using a cryomicoscopy system, change on the solution of phase transition was analysis by the use of differential scanning calorimetry (DSC) instrument. The experiment of cryomicoscopy demonstrates that the shape and size of the crystal of CPA are related to the concentration of the solution and the addition of the solute, small ice crystals cause little damage to the cells with the high concentration, and reduces physical damage to the cellular structure with an appropriate ratio of sorbitol and Me2SO. Furthermore, DSC demonstrates that the mixture of 5%Me2SO and 0.4Msorbitol for cryopreservation achieved a satisfactory outcome , the temperature, the enthalpy, the crystal were even better than other three solution. Therefore the injury of cells has slightest.关键词：DSC;dimethyl-sulfoxide(Me₂SO);sorbitol1978|1977|0发布时间：2024-07-18
- 摘要：The ejector performance is numerically and experimentally investigated using R236fa as working fluid to analyze the influence of the critical geometries of ejector. The ejector used in the simulation has simplified three-dimensional centrosymmetric structure and the Shear Stress Transport（SST）turbulence model has been used. The results show that when the operating parameters conditions are given, both of the length of nozzle outlet (D1) and the distance of nozzle exit to mixing chamber (D2) have an optimal value. At this point, the entrainment ratio reaches the maximum. While the angles of diffuser (α) increase, the performance of ejector decline.关键词：ejector;three-dimensional model;SST model;R236fa1806|1982|0发布时间：2024-07-18
- 摘要：Heat transfer characteristics of Pulsating Heat Pipe (PHP) with fill ratio of 45%, 55%, 62%, 70% were researched experimentally for aqueous ethanol with volume ratio of 13:1, 2:1, 1:1, 1:2, 1:13 as working fluids. Experimental results indicated that, with lower fill ratio, the thermal resistance of aqueous ethanol PHP was better than that of water or ethanol PHP; and with higher fill ratio, the characteristics of heat transfer using water as pure working fluid were better than that of using ethanol pure working fluid or aqueous ethanol fluids. It was found out from experimental results that, the heat transfer characteristics of PHP depended on the fill ratio of working fluids and the volume ratio of the two components which related to vapor-liquid balance, physical properties and the association of molecules.关键词：heat and mass transfer;pulsating heat pipe;mixed working fluids;thermal resistance1902|2017|0发布时间：2024-07-18
- 摘要：The numerical simulation and experimental methods were used to study the efficiency of flow distribution and pressure drop of the micro-channel evaporators with parallel flow. R134a was as the working fluid. The results show that: with the same deflector structure, as the open area of holes in the deflector increased, the pressure drop of the evaporator decreased, while the flow distribution uniformity of refrigerant deteriorated, but the cooling capacity of evaporator is first increased and then decreased. There is an optimum open area of holes in deflector to the micro-channel evaporator with parallel flow, then the pressure drop and flow distribution uniformity get to the best matching, lead to the cooling capacity being the max. For the micro-channel evaporator with parallel flow type, the optimum open area of holes in the first deflector is about 150.7mm2.关键词：micro-channel evaporator;deflector;open area of holes;convective heat transfer2014|2002|0发布时间：2024-07-18
- 摘要：To study the platform piston wind distribution characteristics from the mechanism, it is put forward that the characteristics of platform piston wind conform to the attached jet theory, combining the theory modeling, field measurement and liquid scale model test. Based on the field measurement in a subway station in Shanghai, the field test data fit well with the theory calculation results in the initial segment of platform piston wind. The standard deviation between theory calculation and field measurement is between 0.326 and 0.542. The liquid scale model test is set up to verify the related mathematical model during the boundary layer district, potential flow core area and free shear zone in the initial segment. The model test results have good agreement with theory calculation with the standard deviation between 0.071 and 0.746. It is proved by above research works that the platform piston wind could be taken as the attached jet initial segment.关键词：the platform piston wind;initial segment of the attached jet;field measurement;liquid scale model test1943|1987|0发布时间：2024-07-18
- 摘要：Experiments of an air source heat pump water heater(ASHPWH) using R134a prototype were carried out and analyzed the effects of improper refrigerant charge and incorrect TXV opening on the system. The performance of the system were measured in combinations of four refrigerant charges of 70%，85%，100% and 115% of the optimal value and three TXV opening of 30%, 45% and 60% of full opening at ambient temperature of 20/15℃. The results showed that the system COP was increased to a point and then tended to decrease, the expansion valve opening had a significant impact on performance, it was found that increasing the TXV opening can enhance COP when water temperature above 32°C. Based on the experimental investigations, an exergy analysis was conducted to evaluate the thermodynamic performance of the system and components in this study. It was found that exergy losing of the system was mainly occurred in the compressor and condenser. The system exergy efficiency was decreased with water temperature increased, it was decreased by 8% and 10% respectively when the expansion valve opening was 30% and 60%.关键词：ASHPWH;refrigerant charge;TXV opening;R134a;exergy analysis1918|2101|0发布时间：2024-07-18
- 摘要：Combined the without heat contact resistance technology with different corrugated fins, the new kinds of fin has been developed. The surface heat transfer coefficient and friction coefficient of fins was calculated by CFD software in order to find the different between sharp corner corrugated fins and rounded corner corrugated fins. The sample of heat exchanger was made and the performance was tested in wind tunnel experimental system. Compared the simulation and experiment result, we found that they have good consistency and the errors between them are less than 10%. The simulation result can reflect the real heat transfer situation between the fins of exchanger. Evaluation of heat transfer enhancement was adopted. The result showed that the DEC always bigger than 1 in different wind speed, so the performance of sharp corner corrugated fins is better than rounded corner corrugated fins.关键词：without heat contact resistance;corrugated fins;heat transfer enhancement1846|1919|0发布时间：2024-07-18
- 摘要：Contents of vitamin C(Vc) and total soluble solids(TSS) were determining to analyze the effect of processing like segmentation, blanching and freezing rate on the quality of four kinds of vegetable including potato, carrot, broccoli and onion. The results show that the freezing rate within a certain range shows no significant effect on Vc and TSS of these four vegetables, the larger cuts of vegetables can effectively maintain the content of Vc and TSS and the blanching before quick-freezing causes a greater loss to Vc and TSS of carrots and onions, but it is more suitable for potato and broccoli to maintain the content of Vc and TSS.关键词：blanching;quick-frozen rate;vitamin C;total soluble solid(TSS)2060|1926|0发布时间：2024-07-18
- 摘要：Superheat of evaporator outlet is a symbol of state of air-conditioning, in order to study the effect on the performance of evaporator and system in automotive air-conditioning, a serial experiments have been done. A new kind of valve has been used to control the superheat in the standard automotive air-conditioning bench, and the effect of superheat on the performance has been study. The results show, capacity of evaporator increases with the decreasing of superheat, and it can reach 19.4% in the study’s system. COP increases to a maximum value then decreases with the decreasing of superheat of evaporator outlet，and it can reach 17.8% in the study’s system.关键词：automotive air-conditioning;superheat;capacity;COP2587|2357|0发布时间：2024-07-18
- 摘要：The CFD software was applied to conduct the numerical simulation for predicting the air velocity, pressure, and temperature，humidity ratio in the corrugated filler which was used in evaporative condenser. And then studies on influencing factors of humidity ratio, pressure difference and surface heat transfer coefficient, i.e., filler space, air velocity and mass flux of cooling water were conducted. Simulation results were verified through experiments, and the error was less than 5%. The results showed that with the increasing filler space, humidity ratio of outlet air decreased after the first increase, and pressure difference decreased from 900Pa to 50Pa. Surface heat transfer coefficient increased with increasing air velocity, and humidity ratio of outlet air decreased from 24 g/kg to 23 g/kg. With the increase of mass flux of cooling water, humidity ratio of outlet air changed from 23.1 g/kg to 24 g/kg and surface heat transfer coefficient decreased 15.2 W/（m2?K）to 14.6 W/（m2?K）. It contributed to heat and mass transfer and lower energy consumption when filler space was 6mm, air velocity was 2m/s and mass flux of cooling water was 0.025 kg/s.关键词：evaporative condenser;heat and mass transfer;corrugated filler;numerical simulation13411|12388|0发布时间：2024-07-18
- 摘要：The arrangement configuration of delta wing and elliptical cylinder were cautiously carried out on spiral warped channel wall layers of combination vortex generator. Based on numerical simulation FLUENT to study the influence of three parameters on heat transfer, including assembly distance s, triangle wing angle of attack α and elliptical cylinder angle of attack β which were discussed within the Reynolds number Re range from 4000 to 7000. Then using Orthogonal experiment methods to optimize the vortex generator structure entirely, obtaining the order of priority and optimum composition structure on heat transfer. Comparing with experimental test, the intensified heat transfer effect was reinforced by optimizing structure and normal structure of composite. The results show that α=45°,β=45°,s=90mm can have the comprehensive effect on heat exchanger optimum. what’s more, the intensified heat transfer is higher 18.9%~38.3% than ordinary .Therefore, the accuracy and validity had been confirmed definitely.关键词：heat transfer technology;optimum combination structure;orthogonal test;intensified heat transfer2426|2183|0发布时间：2024-07-18
- 摘要：HFO-1234ze，R22 and R417A were compared with each other from aspect of thermal properties, ODP, GWP, toxicity, flammability and so on. Theoretical feasibility of HFO-1234ze used in heat pump water heater was analyzed through theoretical calculation. A experiment is carried out on the air resource heat pump water heater using HFO-1234ze, R22, and R417a under standard conditions. Suction and discharge pressure, suction and discharge temperature, compressor input power, thermal heating capacity, and coefficient of performance had been analyzed. The result shows that HFO-1234ze has well applicability using in heat pump water heater. This research provides the references for the refrigerant selection of the heat pump water heater.2077|2173|0发布时间：2024-07-18
- 摘要：To find a non-contact method that can reduce the weight loss of food during the vacuum cooling process, the mechanism of the water losing in tuber was studied firstly with the help of a high speed camera. Then, the effect of different depressurization schemes on the water loss in different tubers (with diameters of 27 mm，22 mm and 12 mm respectively) was studied based on the above conclusion. The results show that: 1) most of the lost water is launched out by the taylor bubble in the tube; 2) slowing the vacuum speed suitably while the total pressure is close to the flash point can reduce the weight loss significantly (the decreasing ratio was 72%); 3) using the tube with a smaller diameter can caused a higher weight loss when the pressure is close to the flash.关键词：vacuum cooling;weight loss;pump speed;tube diameter1858|1938|0发布时间：2024-07-18
- 摘要：Experimental studies of boiling heat transfer of R417A on three single horizontal doubly-enhanced tubes have been conducted at the saturation temperature of 8 ℃. A modified Wilson plot technique was used to obtain the boiling heat transfer coefficients, and the thermal resistance analysis was conducted. The results indicate that the intube heat transfer coefficients of the three enhanced tubes are within 2.524-2.658 times as those of smooth tube, which were rolled 0.32-0.34 mm high spiral channel. For the same type of enhanced heat transfer surface, the trends of boiling heat transfer coefficient with the wall temperature difference are similar. Boiling heat transfer coefficients of tube E30 (42 fin per inch) are 4.5 percent higher than those of tube E32(50 fpi) at the same temperature difference. It is indicated that the boiling heat transfer coefficient and its trend were closely related with fin density (pore diameter) and tube type. Boiling heat transfer of R417A on doubly- enhanced tubes, the outer thermal resistance was about 70% of the total thermal resistance, further enhancement was useful for improving the overall heat transfer performance. Boiling heat transfer coefficient of R417A is only one third of R134a at approximate conditions, R134a is the main component of R417A, indicating that the boiling heat transfer of mixed refrigerants are quite different with pure refrigerants.关键词：doubly-enhanced tubes;refrigerant 417A;boiling heat transfer1979|1935|0发布时间：2024-07-18
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