共查询到17条相似文献,搜索用时 187 毫秒
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以竖直盘管直接蒸发内融冰式冰蓄冷空调蓄冰槽内的传热过程为基础,利用热阻网络法和能量平衡建立了融冰过程的数学模型,对其融冰机理进行了理论分析。计算结果表明,融冰过程中蓄冰槽盘管出口的制冷剂温度随时间逐渐升高,但在后期存在一个因冰柱碎裂上浮导致自然对流瞬时得到强化从而引起的短时间轻微下降现象。另外,蓄冰槽内的传热系数经历了先骤然降低,然后维持稳定,最后又快速上升的过程。该现象与盘管外由于冰融化所形成的水环直径有关,水环直径越大,释放冷量的速度就越小。通过与实验数据的对比,验证了计算模型的合理性和准确性。 相似文献
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分时蓄冷时负荷变化大,但可充分利用低谷电来制冰蓄冷,而在高峰时,制冷机不开以融冰供冷,满足空调负荷要求,真正起到在电网中削峰填谷作用。分时蓄冷时,负荷变化大,在融冰循环运行时,流量变化幅度随之变大,情况特殊,因此需要系统要有应对策略。 相似文献
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热管式相变蓄热换热器储/放能过程中传热特性的实验研究 总被引:1,自引:0,他引:1
将热管作为换热元件应用于相变蓄热系统中,研制了一套热管式相变蓄热换热器。采用石蜡作为蓄热材料,对其储、放能过程即内部石蜡的融化与凝固过程进行了实验研究。测定了储、放能过程中不同时刻换热器内石蜡的温度分布; 改变供、取热流体参数,分析了供/取热流体的入口温度与流量对换热器储/放能过程的影响;分析了储、放能过程中能量随时间的变化情况。结果表明,热管在本换热器内极好地发挥了换热元件的作用,换热器运行状况良好,各项功能均能较好地实现。 相似文献
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In this study, Marangoni flow and heat transfer enhancement in a heat pipe have been investigated. The experiments were carried out at different heat inputs. A constant temperature water bath was used at the condenser section at three temperature levels. Heat transfer coefficients and thermal resistances of the heat pipe were measured for pure water and water/butanol solutions. The experimental results confirmed that the heat pipe filled with butanol solutions showed better thermal performance than the water-filled heat pipe. At maximum heat flux, 25% heat transfer improvement was obtained when 7 wt% butanol solution was used instead of pure water. 相似文献
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M. K. Rathod 《实验传热》2013,26(1):40-55
Thermal performance of a latent heat storage unit is evaluated experimentally. The latent heat thermal energy storage system analyzed in this work is a shell-and-tube type of heat exchanger using paraffin wax (melting point between 58°C and 60°C) as the phase change material. The temperature distribution in the phase change material is measured with time. The influence of mass flow rate and inlet temperature of the heat transfer fluid on heat fraction is examined for both the melting and solidification processes. The mass flow rate of heat transfer fluid (water) is varied in the range of 0.0167 kg/s to 0.0833 kg/s (1 kg/min to 5 kg/min), and the fluid inlet temperature is varied between 75°C and 85°C. The experimental results indicate that the total melting time of the phase change material increases as the mass flow rate and inlet temperature of heat transfer fluid decrease. The fluid inlet temperature influences the heat fraction considerably as compared to the mass flow rate of heat transfer fluid during the melting process of the phase change material. 相似文献
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Esad Tombarević & Igor Vu&scaron anović 《advances in applied mathematics and mechanics.》2011,3(3):354-369
Phase change in ice-water systems in the geometry of horizontal
cylindrical annulus with constant inner wall temperature and adiabatic
outer wall is modeled with an enthalpy-based mixture model. Solidification
and melting phenomena under different temperature conditions are
analyzed through a sequence of numerical calculations. In the case of freezing
of water, the importance of convection and conduction as well as the influence
of cold pipe temperature on time for the complete solidification is examined.
As for the case of melting of ice, the influence of the inner pipe wall
temperature on the shape of the ice-water interface, the flow and temperature
fields in the liquid, the heat transfer coefficients and the rate of melting
are analyzed. The results of numerical calculations point to good qualitative
agreement with the available experimental and other numerical results. 相似文献
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Water-spray-cooled quasi-isothermal compressed air energy storage aims to avoid heat energy losses from advanced adiabatic compressed-air energy storage (AA-CAES). The compression efficiency increases with injection water spray. However, the energy-generated water spray cannot be ignored. As the air pressure increases, the work done by the piston and the work converted into heat rise gradually in the compression process. Accordingly, the flow rate of the water needed for heat transfer is not a constant with respect to time. To match the rising compression heat, a time sequence of water-spray flow rate is constructed, and the algorithm is designed. Real-time water-spray flow rate is calculated according to the difference between the compression power and heat-transfer power. Compared with the uniform flow rate of water spray, energy consumption from the improved flow rate is reduced. 相似文献
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《Heat Recovery Systems and CHP》1992,12(1):1-9
A new heat transporter is described, the tiltpipe liquid thermosiphon (TLT). In service, a straight, sealed pipe, filled with liquid, is maintained in a tilted orientation. By means of the contained liquid, heat is received from a heat source at the lower end of the pipe, transported to the elevated end, and delivered to a heat sink. The heat transport rate and the temperature distribution in the TLT were studied over a wide range of tilts, with water as the liquid, contained in a steel pipe. At its optimum tilt the TLT combined a high heat transport rate with virtually no temperature degradation in the water from end-to-end of the pipe. In both of these criteria the TLT far exceeded the performance of the unit in vertical orientation, the only one examined by previous investigators. Another characteristic difference between the tilted and the vertical unit was that at any given pipe cross section in the heat transport region (i.e., between the heat source and the heat sink), the water in the tilted pipe had a higher temperature near the top of the cross-section than near the bottom. With vertical orientation there was no such temperature difference. The experimental results with the TLT, particularly in the region of the optimum tilt, were explainable in terms of a liquid thermosiphon mechanism, but a unique one. It was inferred that there was cyclical countercurrent flow of contiguous streams in a single pipe with a warmer, less dense water stream flowing axially upward through a top segment of the pipe cross-section and, separated by a quiescent interfacial plane, a cooler, more dense water stream flowing axially downward, through a bottom segment. It followed that at the pipe terminals each stream reversed itself, becoming its opposite by virtue of heat receipt/delivery at the heat source/sink. The contiguous, countercurrent flow pattern described above was confirmed visually at the optimum tilt of eleven degrees by observation of water flow inside a clear plastic tube added to the midsection of the steel pipe. The streams were rendered visible by injections of soluble coloring material in the water at the elevated and lowered ends of the pipe. 相似文献