The impact of heat pumps on global warming and ozone depletion

The heat pump, a proven and reliable technology, has the potential to reduce primary energy consumption and the corresponding CO₂-emissions for heating and cooling in domestic, commercial and industrial applications. The basic principles of heat pump technology and the anthrogenic CO₂-formation under the given energy supply and demand situation in Europe and the related impact on global warming are described.An analysis of the energy flow between primary energy exploitation and the useful energy of different heating systems clearly demonstrates the ability of electric heat pumps to reduce primary energy consumption in Europe between 15 and 50%, compared with oil- and gas-heating systems. The corresponding reduction of CO₂-emissions will be between 20 and 60% and up to 85% of other pollutants.The present status of alternative working fluids which do not contribute to ozone depletion is presented and the direct (working fluids) and indirect (energy consumption) impact of different heat pumps on the greenhouse effect is discussed.     

微型冷热电联产系统热力学分析

根据一套10kw级微型分布式冷热电联产系统(采用燃气内燃机发电,地板辐射采暖,吸附制冷机提供空调制冷)在冬夏两季实验研究获得的数据,从热力学第一及第二定律角度,进行热力学分析,与传统的冷、热、电分产系统进行比较,并对不同评价标准得出的结果展开了进一步的探讨。分析揭示了冷热电联产系统高效节能的原因,得出的相关结论为实验系统的改进以及未来实际应用系统的设计,提供了理论依据.     

Resedential space conditioning with solid sorption technology

Approximately 50% of residential energy use in the U.S. is for space heating and cooling. The most popular type of system installed in U.S. houses is a central air-circulating system combining a natural-gas-fired direct-air-heating furnace and an electric-driven vapor compression cooling system. Natural-gas-driven heat pump technology offers considerable benefits over these existing technologies including a reduction in energy use, improved environmental impact, and reduced investment in electric power plant construction. However, over the past 30 years, more than 100 major natural-gas-driven heat pump development projects have been undertaken without a currently successful product. These past projects have focused on engine-driven vapor compression refrigeration cycles and liquid sorption refrigeration cycles. New solid sorption technology offers significant advantages over these engine and liquid sorption technologies. The fundamental advantages of solid sorption refrigeration technology in natural gas residential heat pumps are presented and the societal benefits over existing residential systems discussed.     

Economic comparison between adsorption and compression heat pumps

Adsorption and electric heat pumps have been compared for domestic heating and cooling for three Italian cities: Messina, Rome and Milan. The daily energy needs based on the characteristics of a flat and on the meteorological data of the cities have been calculated. From heating and cooling efficiencies of the electric and adsorption heat pumps the electric and gas energy consumption have been evaluated and compared. Finally, the annual cost of the electric heat pump has been estimated and from this, the maximum available cost of the adsorption machine is presented for each city.The final results show that adsorption heat pumps represent an energy saving machine with a good economic competitivity with respect to the traditional system.     

Heat pipes for ground heating and cooling

Different versions of heat pipe ground heating and cooling devices are considered. Solar energy, biomass, ground stored energy, recovered heat of industrial enterprises and ambient cold air are used as energy and cold sources. Heat pipe utilization of air in winter makes it possible to design accumulators of cold and ensures deep freezing of ground in order to increase its mechanical strength when building roadways through the swamps and ponds in Siberia. Long-term underground heat storage systems are considered, in which the solar and biomass energy is accumulated and then transferred to heat dwellings and greenhouse, as well as to remove snow from roadways with the help of heat pipes and solar collectors.     

Square wave analysis of the solid-vapor adsorption heat pump

A thermally driven heat pump using a solid/vapor adsorption/desorption compression process in a vapor compression cycle is thermodynamically analyzed. The cycle utilizes a simple heat transfer fluid circulating loop for heating and cooling two solid adsorbent beds. This heat transfer fluid loop also serves to transmit heat recovered from the adsorbing bed being cooled to the desorbing bed being heated. This heat recovery process greatly improves the efficiency of the single stage solid/vapor adsorption process without the complication of a two stage cycle. During the heating and cooling processes a thermal wave profile travels through the beds. This paper uses a square wave representation for the true shape of the thermal wave. However, this square wave is assumed to stop short of the bed ends to account for realistic finite waveforms. The square wave model is integrated into a thermodynamic cycle which provides detailed information on the performance of the beds as well as the COP and the heating and cooling outputs of the heat pump system. Significant cycle design and operating parameters are varied to determine their effect on cycle performance.     

主动式冷却系统微型化发展现状

常规的制冷系统在一些特殊场合下不能用作消除热害的理想解决方案.得益于微系统工艺和微尺度传热传质理论的不断完善,以蒸气压缩系统、吸收式系统和热电系统为代表的主动冷却系统在微型化和轻量化方面取得显著进展.文中基于国内外最新文献分别介绍了这三种主动冷却系统的优、缺点及发展现状,通过实例对比说明蒸气压缩系统具有较大发展潜力,就...     

Techno-economic viability of upgrading thermal effluents in industries: Application in developing countries

Upgrading industrial thermal effluents using a heat pump is an effective energy conservation measure. Although it is proven and has been in use in industrialized countries, its application is grossly lacking in the developing world.Using technical and economical parameters, this paper investigates the viability of upgrading industrial thermal effluents and hence conserving energy using different types of heat pumps. Eleven different types of systems are formulated using the mathematical models developed for multi-stage vapor compression heat pumps and multi-stage vapor jet compressors and adopting the “Grossman Absorption Model” for the absorption heat transformer. A comparative analysis is performed for upgrading the low temperature industrial thermal effluents by employing various types of heat pumps with presently existing fuel and electricity prices in Thailand. It does not take into account the process details or the heat pump integration details. A case of integrating heat pumps in distillation columns in an industrial plant in Sri Lanka is also investigated. The energy saving potential clearly indicates that heat pumps are techno-economically viable in the industries of developing countries. The absorption heat transformer is very attractive since it utilizes waste heat itself to upgrade the thermal effluent temperature.     

Thermodynamic analysis and design data for a double-effect absorption heat pump system using four working pairs

Performance analysis of a double-effect absorption heat pump system has been done for water-four working pairs (or mixture) by computer simulation. The coefficient of performance and mass flow ratio are investigated to compare these aqueous solutions [waterLiCl, waterLiBrLiBr waterLiClCaCl₂Zn(NO₃)₂] which was developed for only cooling, with conventional waterLiBr solution, based on mass, material and heat balance equations for each part.From this analysis, it is found that the performances of the new aqueous solutions are better than that of LiBrwater solution not only in cooling systems, but also in heating systems, although the operating temperature ranges of these new aqueous solutions are very narrow in heating. Theoretical thermodynamic performance data can be used and are given here by design data.     

An open cycle absorption heat pump

The absorption cycle can be also of the open type. This concept has been utilized in developing solar cooling absorption systems. Another possibility not yet investigated is an open cycle absorption heat pump. The system rests upon the utilization of a packed tower operating with liquid desiccants. The tower dehumidifies both the exhausted air of heating plant and the exhaust of a natural gas boiler. A conventional heater heats up the regenerator of the sorbent and the inlet air. Simulations give a PER of the system (the open cycle heat pump) higher than 1.3 with respect to the Gross Calorific Value of natural gas. This value is difficult to obtain with the more complex closed cycle absorption or vapour compression cycle motor driven heat pump.     

Two case studies of cogeneration systems design and economic feasibility

Cogeneration is an ideal method of power production for applications which require both heat and power simultaneously, hence the name combined heat power (CHP). In this paper, design studies of cogeneration systems for two specific applications are presented. The results indicate the economic feasibility of such installations and how much energy can be saved, especially if the system is analysed on a long-term basis. It is shown that an essential requirement for cogeneration is the proper matching of power and heat demands.The first design study is of a combined power and heating system for a small suburban hospital which requires both steam and power for its various needs. The cogeneration system which was designed for this application consisted of a conventional turbo-charged spark ignition engine with heat exchange from its exhaust and engine cooling systems, coupled with an existing boiler. When the cogeneration system is inadequate to meet the electricity demands, the excess power would be bought from the grid supply. For an initial outlay of approximately $250,000 (1990 prices), an annual saving of $140,000 was conservatively predicted, with an internal rate of return of some 40% over 15 yr.The second design study is for the energy system of a large sugar confectionery factory with power and heat requirements, mainly for lighting, air conditioning and several manufacturing processes. The hardware which was chosenfor the cogeneration system for this case comprises a diesel engine converted for use with natural gas connected to a vertical shell and tube exhaust gas boiler. For an initial investment of approximately $700,000, an annual saving of about $130,000 (1991 prices) is predicted for a 10–15 yr project. The savings and the payback period depend on the electricity buy-back tariffs and the company's plans for future expansion.     

Performance and Exergy Analyses of a Solar Assisted Heat Pump with Seasonal Heat Storage and Grey Water Heat Recovery Unit

The main research objective of this paper was to compare exergy performance of three different heat pump (HP)-based systems and one natural gas (NG)-based system for the production of heating and cooling energy in a single-house dwelling. The study considered systems based on: 1. A NG and auxiliary cooling unit; 2. Solely HP, 3. HP with additional seasonal heat storage (SHS) and a solar thermal collector (STC); 4. HP with SHS, a STC and a grey water (GW) recovery unit. The assessment of exergy efficiencies for each case was based on the transient systems simulation program TRNSYS, which was used for the simulation of energy use for space heating and cooling of the building, sanitary hot water production, and the thermal response of the seasonal heat storage and solar thermal system. The results show that an enormous waste of exergy is observed by the system based on an NG boiler (with annual overall exergy efficiency of 0.11) in comparison to the most efficient systems, based on HP water–water with a seasonal heat storage and solar thermal collector with the efficiency of 0.47. The same system with an added GW unit exhibits lower water temperatures, resulting in the exergy efficiency of 0.43. The other three systems, based on air–, water–, and ground–water HPs, show significantly lower annual source water temperatures (10.9, 11.0, 11.0, respectively) compared to systems with SHS and SHS + GW, with temperatures of 28.8 and 19.3 K, respectively.     

用低温粉碎法生产精细胶粉技术的进展

资源的再利用是一项保护地球有限资源的重要措施。文中介绍了两种用于生产精细胶粉的高效制冷系统 :空气涡轮膨胀制冷系统和氨 -乙烷复叠式制冷系统。这两种方法都具有能耗低、产量高、胶粉细度好等优点。     

跨临界二氧化碳蒸气压缩/喷射制冷循环性能比较

本文从系统的COP、制冷量和有效能分析三个方面比较了跨临界CO2蒸气压缩／喷射循环、蒸气压缩／回热制冷循环和常规的蒸气压缩制冷循环的性能．结果表明,在本文研究工况下,喷射循环的性能系数最大值比回热循环高 18．6％,比常规循环高22．0％．喷射循环的制冷量比回热循环高8．2％,比常规循环高11．5％。有效能分析表明喷射循环极大地减小了节流损失,冷却放热损失和压缩损失也有相应的减少．     

Impact of urbanization and climate warming on energy consumption in large cities

This article considers the urban heat island effect, taking into account peculiarities of energy consumption in large cities. It is shown that energy demand in large cities must be planned, taking into account of the seasonal asymmetry of the impact of anthropogenic heat fluxes on energy demand of the urban economy in the warm and cold seasons of the year. Together with the heat island effect, climate changes in Russian cities should decrease the overall energy demand due to space heating and air conditioning. At the same time, the increasing energy share used for air conditioning always remains one or two orders of magnitude smaller than the energy share used for space heating.     

热源塔热泵系统夏季工况优化运行实验研究

由于热源塔在冬夏季工况下的换热能力存在较大差异,按冬季工况设计的热源塔热泵系统,在夏季工况下运行时存在换热能力过剩的问题,影响系统性能。为解决上述问题,本文构建了热源塔热泵系统,实验研究了其冬夏季工况的性能差异。在此基础上,对夏季工况下的优化运行进行了实验研究,结果表明,通过调节空气和溶液流量,将热源塔的逼近度和冷幅分别控制在3.5℃和4.3℃,可使得系统性能系数由3.6提升至3.9,并对其节能机理进行了分析。     

非晶材料玻璃转变过程中记忆效应的热力学

低温下处于非平衡态的非晶材料升温到玻璃转变以上,要先后发生弛豫和回复最终达到平衡过冷液态,其中弛豫过程中释放的能量在回复过程中以等量的方式获取,表现出明显记忆行为.本文基于氧化物、金属与小分子等多种非晶形成体系,全面探讨了在围绕玻璃转变的一个冷却加热循环过程中的焓弛豫特征,建立了弛豫谱,发现弛豫焓在数值上与熔化焓密切相关.基于弛豫焓与非晶材料动力学Fragility之间的关联,展示了非晶体系在动力学极限(m=175)条件下的玻璃转变热力学基本特征,与热力学二级相变进行了对比.研究深化了对非晶弛豫与玻璃转变热力学的理解.     

Start-stop control strategies for heat recovery in multi-zone water-loop heat pump systems

A study is made to determine the energy saving potential of a start—stop controlled water-loop heat pump (WLHP) system. The physical model consists of individual heat pumps for each zone, a two-pipe water-loop system (with and without a storage tank), a boiler and an evaporative cooler. The overall system consists of four input energy controllers and an equal number of mass flow rate controllers. A simple start-stop control strategy for the system is developed. Results showing the typical daily operation of the system under changing heating and cooling loads are presented. A method for selecting the appropriate limits for loop water temperature which results in energy savings is given.     

振荡流热管振荡相变传热特性

本文建立了环路型振荡流热管物理数学模型。数值计算结果表明,汽泡的交替膨胀和压缩使管内工质维持振荡运动,热管冷却端的散热情况是影响振荡流热管内部振荡运动的重要因素。热管内部振荡运动受倾角、充液率和加热功率影响,其变化趋势与前期实验结果基本一致。热管内脉动运动愈剧烈,热管的传热性能愈好。     

1.x级溴化锂吸收式制冷循环性能分析

提出了一个适合于利用太阳能的新型1.x级溴化锂吸收式制冷循环。计算了该循环的性能。结果表明,在现有太阳能集热器所能提供的热水温度范围,1.x级循环克服了单效循环运行范围窄的缺点,其性能指标明显高于两级循环;冷却水先进入冷凝器的串联流程优于并联流程;热水、冷媒水、冷却水温度对溴冷机循环系统的性能系数、热源单耗、面积单耗等经济性指标有较大影响。