冰源热泵系统在设施水产养殖中的技术经济性研究

针对目前刺参养殖的水温调控系统能耗大及适用性差等问题,提出基于冰源热泵的高效清洁供热及结合跨季节蓄冷实现全年冷热管理的技术思路,采用冰源热泵系统和跨季节蓄冷型冰源热泵系统对养殖水体温度进行调控,建立模型定量对比分析系统的运行能效及技术经济性.结果表明:(1)冰源热泵系统供热和供冷时的性能系数分别为3.33和3.39,全...     

Experimental and analytical study on thermoelectric self cooling of devices

This paper presents and studies the novel concept of thermoelectric self cooling, which can be introduced as the cooling and temperature control of a device using thermoelectric technology without electricity consumption.For this study, it is designed a device endowed with an internal heat source. Subsequently, a commonly used cooling system is attached to the device and the thermal performance is statistically assessed. Afterwards, it is developed and studied a thermoelectric self cooling system appropriate for the device.Experimental and analytical results show that the thermal resistance between the heat source and the environment reduced by 25-30% when the thermoelectric self cooling system is installed, and indicates the promising applicability of this technology to devices that generate large amounts of heat, such as electrical power converters, transformers and control systems. Likewise, it was statistically proved that the thermoelectric self cooling system leads to significant reductions in the temperature difference between the heat source and the environment, and, what is more, this reduction increases as the heat flow generated by the heat source increases, which makes evident the fact that thermoelectric self cooling systems work as temperature controllers.     

间歇性大功率相变热沉研究

针对某300W大功率间歇式热源,选用9wt%膨胀石墨-56号石蜡复合材料作相变工质,铝翅片作导热结构,基于Fluent软件,采用等效比热容数学模型,在安全温度为65℃情况下,设计得到能稳定运行3500s的相变热沉。针对该相变热沉,为验证等效比热容数学模型的可靠性,搭建了相变热沉测试系统,研究了热源功率及相变工质对热沉控温性能的影响。结果表明：等效比热容数学模型有效可靠;相变材料熔点越低,相变热沉温控时间越长;而热源输入功率越高,相变工质熔点的影响将变小。此外,为降低系统内部温差、减少石蜡泄露以及降低加工成本,进一步提出了热管-回转式翅片相变热沉,热管-回转式翅片相变热沉在热源功率为300W条件下,温控时间高达4300s,内部温差仅在1.6℃以内。     

Performance analysis of a heat pump assisted drying system

The paper describes a simulation model developed to predict the performance of drying systems assisted by vapour-compression heat pumps. The heat is used to preheat the air stream before it enters the drying chamber. Energy consumption is thus reduced, as the heat pump is capable of delivering more energy as heat than it in fact consumes as input work. Ambient air provides the heat source. A computer program, based on simplified modelling of components (compressor, heat exchangers and drying chamber) has been developed. Results have been produced for a typical application, revealing that a considerable reduction in energy consumption can be obtained with the use of a heat pump. The effect of air flow rate on system performance is also studied.     

Study of heat and mass transfer in integrated thermal management controller (ITMC) employed in waste heat recovery application

In the waste heat recovery process, heat source temperature control and thermal management are always required to ensure safety and high efficiency of the waste heat recovery system. To this aim, the conventional method is to establish a series of independent heat transfer units and adopt a complex control strategy, which makes the system very complex and only applicable for a specific object. The concept of “integrated thermal management controller” (ITMC) is presented in this work to provide a novel method to solve the above problems. A two-dimensional heat and mass transfer model is developed to analyze and predict the operation performance of the ITMC. The numerical analysis indicates good heat source temperature control and thermal management performance of the ITMC. In addition, an experimental prototype is established, and test data are presented, which agree well with the numerical results and verify the correctness of the model.     

基于线热源理论的垂直U型埋管换热器传热模型的研究

基于经典常热流线热源理论,通过引入叠加原理、阶跃负荷及孔洞热阻思想将其发展为能够适用于变热流埋管换热与地源热泵系统模拟的变热流线热源模型,并与改进的经实验与理论验证的圆柱源理论模型进行了比较与分析。结果表明:所发展的变热流线热源模型能够有效地模拟地下埋管的换热过程,可作为地下垂直U埋管换热过程的计算模型,为地源热泵地下埋管换热器的设计计算及地源热泵系统的模拟提供了一种新的简单而又实用的计算方法。     

Energy and exergy analysis of fossil plant and heat pump building heating system at two different dead-state temperatures

In this paper, we deal with the energy and exergy analysis of a fossil plant and ground and air source heat pump building heating system at two different dead-state temperatures. A zone model of a building with natural ventilation is considered and heat is being supplied by condensing boiler. The same zone model is applied for heat pump building heating system. Since energy and exergy demand are key parameters to see which system is efficient at what reference temperature, we did a study on the influence of energy and exergy efficiencies. In this regard, a commercial software package IDA-ICE program is used for calculation of fossil plant heating system, however, there is no inbuilt simulation model for heat pumps in IDA-ICE, different COP (coefficient of performance) curves of the earlier studies of heat pumps are taken into account for the evaluation of the heat pump input and output energy. The outcome of the energy and exergy flow analysis at two different dead-state temperatures revealed that the ground source heat pumps with ambient reference have better performance against all ground reference systems as well as fossil plant (conventional system) and air source heat pumps with ambient reference.     

Performance study on heat and moisture transfer in soil heat charging

In some cold areas, the system performance of the soil source heat pump system is reduced by the decreasing underground soil temperature, which is caused by the thermal imbalance between the heating demand in winter and the cooling demand in summer. Soil heat charging with solar energy in non-heating seasons is proposed for solving the problem. It has been found from previous studies that the effect of the moisture transfer on the heat transfer within porous media could not be neglected especially under higher temperature difference. Therefore, this paper provides an investigation on the heat and moisture transfer in soil during soil heat charging at high temperature. A numerical model is developed for the study. The simulation results are compared with the testing data from the authors' previous study for the model verification. Based on the verified model, the performance of the heat and moisture transfer in soil during soil heat charging in a longer time and a larger area is investigated in the paper. The results show that the testing data match very well with the simulation results within a relative error of ±9% and the mathematical model is reliable for the performance prediction of heat and moisture transfer in soil heat charging. The soil volumetric water content (VWC) distribution tends to be stable after soil heat charging for 13 days and the heat source has an effective influence on soil VWC distribution within 2.4?m. The effect of the heat source temperature and initial VWC on the soil temperature and VWC distribution and heat power is proved to be obvious. Loam has a better performance in soil heat charging than sand.     

土壤源空调系统全年运行设计与计算分析

采用贝塞尔函数求解了U型埋地换热器在稳态和正弦波边界下的解析解,可计算给定全年动态负荷下埋地换热器内流体温度,并据此判断埋地换热器的设计能否满足建筑物的要求.给出了在不同因素影响下流体全年最高温度和最低温度与U型管单位长度设计取冷(热)量的关系曲线,可用于指导U型埋地换热器的设计.得到了建筑物全年累计耗热量和耗冷量、最大热负荷和冷负荷应满足的关系,可用于指导建筑物冷热源方案的搭配.     

Year round experimental study on a constant temperature and humidity air-conditioning system driven by ground source heat pump

Numerous studies about the ground source heat pump building heating and cooling systems have been constructed in office building, hotel, residential building and school et al. However, few researches about the constant temperature and humidity air-conditioning system driven by ground-coupled heat pumps were carried out. In this paper, a constant temperature and humidity air-conditioning system driven by ground source heat pump was designed and constructed in an archives building in Shanghai, China. During the operation in the cooling mode, the heat extraction from the condenser of the heat pump was divided: part was rejected to the soil while another was used to reheat the air in AHUs. According to the experimental results, the indoor temperature and relative humidity fulfilled the “Archives Design Code”. In summer, the heat rejected to the soil was reduced by 32%, which was helpful for the earth energy conservation. The soil temperature increased only 0.5 °C after the GSHP system operating for a year. The energy cost of the air-conditioning system was 56.1 kWh/m². Compared with air source heat pump system and water cooled unit with boiler system, the operating cost of ground source heat pump was reduced by 55.8% and 48.4%, respectively.     

Dynamic modeling and optimal control strategy of waste heat recovery Organic Rankine Cycles

Organic Rankine Cycles (ORCs) are particularly suitable for recovering energy from low-grade heat sources. This paper describes the behavior of a small-scale ORC used to recover energy from a variable flow rate and temperature waste heat source. A traditional static model is unable to predict transient behavior in a cycle with a varying thermal source, whereas this capability is essential for simulating an appropriate cycle control strategy during part-load operation and start and stop procedures. A dynamic model of the ORC is therefore proposed focusing specifically on the time-varying performance of the heat exchangers, the dynamics of the other components being of minor importance. Three different control strategies are proposed and compared. The simulation results show that a model predictive control strategy based on the steady-state optimization of the cycle under various conditions is the one showing the best results.     

Study on the decision-making of district cooling and heating systems by means of value engineering

A district cooling and heating (DCH) system can provide both cooling and heating for blocks of buildings in cold climate areas, however, different thermal source schemes of a DCH project always differ in their first cost, operating cost, maintenance cost, regulation performance, control performance, energy-saving and environment protection performance, etc. In order to evaluate various DCH thermal source schemes quantitatively, the paper firstly establishes an evaluation model based on value engineering theory. It then elaborates on how this model is applied in the first seawater source heat pump DCH project in China—Dalian Xinghai Bay project. The calculation results show that even though the scheme of seawater source heat pump system is not economical under commercial electricity price mainly because of its relatively high initial cost, yet it has the highest value coefficient under civil electricity price. This also implies that privileges of policy for renewable energy utilization system are necessary to help promote the energy-saving and environment-friendly scheme of seawater source heat pump system.     

Thermodynamic and thermoeconomic analyses of an irreversible combined Carnot heat engine system

A combined cycle model which includes the irreversibilities of finite‐rate heat transfer in heat‐exchange processes and heat leak loss of the heat source is used to analyse the performance of a multi‐stage Carnot heat engine system. The efficiency, power output, ecological function and profit of operating the combined system are optimized. The optimally operating region of the combined system is determined. The optimal combined conditions between two adjacent cycles in the combined system are obtained. Moreover, the cycle model is generalized to include the internal irreversibilities of the working fluids so that the results obtained here become more general. Copyright © 2001 John Wiley & Sons, Ltd.     

基于PID-二分组合控制算法的分布参数空气源热泵仿真模型的研究

采用分布参数法建立双级压缩空气源热泵系统热力学模型,建立一种基于PID-二分组合控制算法的全系统循环分布参数模型,并结合实验数据验证该模型的准确性。结果表明：系统模型在双级压缩制热模式下制热性能系数（COP）的模拟数据与实验数据的平均偏差为5.41%,两者在不同运行模式下的最大偏差不超过15%,均在可信范围之内,模型能准确反映系统性能随外界参数变化的规律;该模型与单独使用比例积分微分（PID）控制算法的分布参数法模型相比,总迭代次数较原模型减少约2.96倍,极大减少了模型的计算量,可在保证模型精度的情况下提升模型的计算速度。     

Thermal slip and radiative heat transfer effects on electro‐osmotic magnetonanoliquid peristaltic propulsion through a microchannel

A mathematical study is described to examine the concurrent influence of thermal radiation and thermal wall slip on the dissipative magnetohydrodynamic electro‐osmotic peristaltic propulsion of a viscous nanoliquid in an asymmetric microchannel under the action of an axial electric field and transverse magnetic field. Convective boundary conditions are incorporated in the model and the case of forced convection is studied, that is, thermal and species (nanoparticle volume fraction) buoyancy forces neglected. The heat source and sink effects are also included and the diffusion flux approximation is employed for radiative heat transfer. The transport model comprises the continuity, momentum, energy, nanoparticle volume fraction, and electric potential equations with appropriate boundary conditions. These are simplified by negating the inertial forces and invoking the Debye–Hückel linearization. The resulting governing equations are reduced into a system of nondimensional simultaneous ordinary differential equations, which are solved analytically. Numerical evaluation is conducted with symbolic software (MATLAB). The impact of different control parameters (Hartmann number, electro‐osmosis parameter, slip parameter, Helmholtz–Smoluchowski velocity, Biot numbers, Brinkman number, thermal radiation, and Prandtl number) on the heat, mass, and momentum characteristics (velocity, temperature, Nusselt number, etc) are presented graphically. Increasing Brinkman number is found to elevate temperature magnitudes. For positive Helmholtz–Smoluchowski velocity (reverse axial electrical field) temperature is strongly reduced, whereas for negative Helmholtz–Smoluchowski velocity (aligned axial electrical field), it is significantly elevated. With increasing thermal slip, nanoparticle volume fraction is also increased. Heat source elevates temperatures, whereas heat sink depresses them, across the microchannel span. Conversely, heat sink elevates nanoparticle volume fraction, whereas heat source decreases it. Increasing Hartmann (magnetic) parameter and Prandtl number enhance the nanoparticle volume fraction. Furthermore, with increasing radiation parameter, the Nusselt number is reduced at the extremities of the microchannel, whereas it is elevated at intermediate distances. The results reported provide a good insight into biomimetic energy systems exploiting electromagnetics and nanotechnology, and, furthermore, they furnish a useful benchmark for experimental and more advanced computational multiphysics simulations.     

基于预测的复合地源热泵系统控制方法实现

在冬冷夏热且夏季冷负荷远大于冬季热负荷的地区常采用带有冷却塔的复合式地源热泵系统,其控制策略存在极大的优化空间。文章提出了直接比较冷却塔和与土壤换热器相连的板式换热器的出口温度的控制方法,并通过人工神经网络预测板式换热器机组侧的出口水温来实现此控制方法。通过FLUENT软件建立复合式地源热泵系统动态数值模型,获取建立神经网络的数据,采用3层BP网络,建立了多个预测板式换热器机组侧出口温度的模型。研究结果表明,采用神经网络可以准确实现此预测,绝对误差不超过0.4℃。     

A new model and solutions for a spiral heat exchanger and its experimental validation

A spiral heat exchanger was applied in a ground source heat pump (GSHP) system that is primarily used for residential indoor heating. Studies that have been performed on the heat transfer of spiral heat exchanger have focused on field measurements and numerical analysis; however, theoretical research on the subject is absent in the literature. In this study, a methodology is proposed to analyze the heat performance of a spiral heat exchanger. A ring source model was established and solved analytically to describe the temperature variation of the ground caused by a spiral heat exchanger. The validity of the model was examined by an experiment on the soil temperature variation with a spiral heater. The virtual ring tube surface temperature response of unit ring circle was calculated by a superposition of the contributions of the ring source itself and adjacent ring sources. Furthermore, a fast algorithm was created to compute the average tube surface temperature resulting from the dimensionless temperature rise at a point far from the ring source that is constant when the non-dimensional distance is less than 0.13. The author confirmed that the calculation time of this proposed algorithm decreased by a factor of 100 compared with the traditional integration method. A system designer will find this algorithm helpful when determining the size of a heat exchanger under a required heating load, particularly for different arrangement of spiral heat exchangers.     

Optimisation for interconnected energy hub system with combined ground source heat pump and borehole thermal storage

Ground source heat pumps (GSHP) give zero-carbon emission heating at a residential level. However, as the heat is discharged, the temperature of the ground drops, leading to a poorer efficiency. Borehole inter-seasonal thermal storage coupled with GSHP maintains the efficiency at a high level. To adequately utilize the high performance of combined GSHP and the borehole system to further increase system efficiency and reduce cost, such a combined heating system is incorporated into the interconnected multi-carrier system to support the heat load of a community. The borehole finite element (FE) model and an equivalent borehole transfer function are proposed and respectively applied to the optimisation to analyze the variation of GSHP performance over the entire optimisation time horizon of 24 h. The results validate the borehole transfer function, and the optimisation computation time is reduced by 17 times compared with the optimisation using the FE model.     

考虑源荷不确定性的电热系统联合调度

针对风电和电热负荷不确定的问题,提出计及源荷不确定性的旋转备用容量的优化方法,建立考虑电热备用耦合影响的调度模型.在日前阶段,以能源与负荷的预测量制定机组的出力方案,风电由于其预测精度较低,利用Beta概率密度函数来拟合风电出力,从而确定风电的不确定性带来的旋转备用容量,利用机会约束规划来处理不确定问题;负荷有较高的预...     

基于圆柱热源模型的现场测量地下岩土热物性方法

在埋地换热器圆柱热源模型的基础上采用参数估计法建立了一套可用于现场确定土壤热物性的方法。结合地源热泵系统单井热响应测试实验,计算了地下岩土热物性参数,模拟了管内流体平均温度随时间变化规律,与实验值比较,发现该方法较线热源法更加接近实际。