Heat pump dryer Part 3: experimental verification of the simulation

Heat pump dryer (HPD) performance described by computer simulation results in Parts 1 and 2 of this series of papers is here verified by experiments. An HPD designed to be operated in four configurations—two open systems and two partially closed systems—has been built. The variables in the experiments are the air flow rate, the dryer load, the ambient condition (day and night) and, for the partially closed systems, the recirculation air ratio and the evaporator bypass air ratio. The parameters used for the verification are the compressor power, the properties of air entering the dryer, the coefficient of performance, the moisture extraction rate and the specific moisture extraction rate. It is found that the experimental results agree with the simulation results within an acceptable error tolerance. In order to predict the HPD performance accurately, a fine tuning of the compressor model and the pressure drop in two-phase flow of the refrigerant are recommended. © 1997 by John Wiley & sons, Ltd.     

Heat pump assisted continuous drying part 1: Simulation model

The addition of a heat pump to a conventional hot air drying system can enhance the efficiency of drying. To investigate the performance of heat pump assisted continuous drying system a detailed simulation model has been developed. The system modelled consists of a vapour compression heat pump coupled to a continuous cross-flow dryer. The model takes account of detailed heat and mass transfer phenomena taking place in each component of the system and can be used to investigate many different system configurations.     

HEAT PUMP DRYER PART 2: RESULTS OF THE SIMULATION

Heat pump dryer characteristics of four configurations, two open and two closed systems, are presented. The results are based on the simulation models developed in Part 1. Emphasis is given to the effects of ambient conditions, recirculating air ratio and evaporator bypass air ratio on the system performance. The criteria for evaluating the system performance are the specific moisture extraction rate (SMER), the moisture extraction rate (MER) and the coefficient of performance (COP). It was found that the ambient conditions and dryer efficiency play an important role in the system behaviour. Optimum performance achieved for one ambient condition cannot be assumed optimum for the others. The recirculating air ratio substantially affects the system performance while the evaporator bypass air ratio shows insignificant effect. © 1997 by John Wiley & Sons, Ltd.     

Performance study of a heat pump dryer system for specialty crops—Part 1: Development of a simulation model

This research is concerned with the technology of heat pump assisted drying of specialty crops. A simplified procedure for modelling the performance of a low temperature heat pump dryer was developed. The system modelled consists of a vapour compression heat pump coupled to a continuous cross flow bed dryer. The model takes into account the detailed heat and mass transfer phenomena taking place in the heat pump and dryer circuits. Copyright © 2002 John Wiley & Sons, Ltd.     

Performance study of a heat pump dryer system for specialty crops—Part 2: Model verification

The experimental and predicted performance data of a heat pump dryer system is reported. Chopped alfalfa was dried in a cabinet dryer in batches and also by emulating continuous bed drying using two heat pumps operating in parallel. Results showed that alfalfa was dried from an initial moisture content of 70% (wb) to a final moisture content of 10% (wb). The batch drying took about 4.5 h while continuous bed drying took 4 h to dry the same amount of material. The average air velocity inside the dryer was 0.36 m s^?1. Low temperatures (30–45°C) for safe drying of specialty crops were achieved experimentally. The heat pump drying system used in this study was about 50% more efficient in recovering the latent heat from the dryer exhaust compared to the conventional dryers. Specific moisture extraction rate (SMER) was maximum when relative humidity stayed above 40%. The dryer was shown to be capable of SMER of between 0.5 and 1.02 kg kW^?1 h^?1. It was concluded that continuous bed drying is potentially a better option than batch drying because high process air humidity ratios at the entrance of the evaporator and constant moisture extraction rate and specific moisture extraction rate values can be maintained. An uncertainty analysis confirmed the accuracy of the model. Copyright © 2002 John Wiley & Sons, Ltd.     

双热源热泵系统模拟研究

基于太阳能热泵和地下水源热泵的优缺点,本文提出了双热源热泵系统。对该系统的各种不同运行工况进行了分析研究,并针对天津地区进行了模拟计算。结果表明：与地下水源热泵相比,在制热量和COP大致相当的情况下,节水量可以达到70％。     

Modeling of a hazelnut dryer assisted heat pump by using artificial neural networks

The artificial neural network (ANN) approach is generic technique for mapping non-linear relationships between inputs and outputs without knowing the details of these relationships. In this paper, an application of the ANN has been presented for a PID controlled heat pump dryer. In PID controlled heat pump dryer, air velocity changed according to the temperature value which is set in process control device. Heat pump dryer was tested drying of hazelnut at 40 °C, 45 °C and 50 °C drying air temperatures. By training the experiment results with ANN, drying air velocities, moisture content of hazelnuts and total drying time were predicted for 42 °C, 44 °C, 46 °C and 48 °C drying air temperatures.     

地源热泵垂直埋管的传热模型及计算

建立了垂直埋管地源热泵地热换热器的传热模型,采用有限差分法建立了垂直U型埋管换热器瞬态传热模型的解析解;并且在不同的工况下进行实验测试,与模拟结果进行了对比,结果表明模拟与实验能较好地吻合,从而使模型的正确性得到了验证。可为地源热泵的设计和运行提供理论指导。     

Optimizing efficiency and productivity of a dehumidifier batch dryer. Part 1: capacity and airflow

A whole dryer model has been used to investigate the influence of the system design on the efficiency and productivity of a batch‐type dehumidifier dryer. The product is an easy‐to‐dry timber, Pinus radiata. The model, which has been validated at both the dryer and dehumidifier levels, includes sub‐models for the whole dryer energy balance, control of preheating, temperature and relative humidity, and the airflow system. The dynamic response of the system is illustrated and the influence of the dehumidifier capacity and the kiln airflow rate on the dryer performance is established. The effect of varying the airflow system losses is also determined. On the whole, drying speed and operating income increase with the dehumidifier capacity and the kiln airflow rate. The energy used by the dryer in a complete drying cycle is strongly influenced by the fan power requirements, and the airflow system losses have a significant adverse effect on the operating income. The results demonstrate the importance of balancing the dehumidifier and the airflow system losses in order to obtain an optimum combination of drying speed and energy efficiency. Copyright © 2000 John Wiley & Sons, Ltd.     

热泵干燥装置的节能研究

对热泵干燥装置混合工质进行优选,建立典型热泵干燥装置结构数学模型,研究提出目标函数并开发出适合热泵干燥结构的程序算法。     

Heat pump assisted distillation. V: A feasibility study on absorption heat pump assisted distillation systems

The problems in matching a heat driven absorption heat pump to a distillation process in heat pump assisted distillation are discussed. The performance of an absorption system is a function of the temperatures in the evaporator, the condenser, the absorber and the generator and the ratio of the mass flow rate in the secondary circuit to the mass flow rate in the primary circuit. In absorption systems design choices are limited by the Gibbs phase rule. Plots are given of the coefficient of performance against the temperatures of the top and bottom products and also against the energy saved.     

空气源热泵热水机组系统仿真的研究

建立了空气源热泵热水机组的系统仿真流程,给出了机组四个主要部件的稳态仿真数学模型,进行变工况稳态工作性能预测,同时给出了换热器中的换热关联式模型。稳态仿真结果与21组实验数据相比,机组运行特性与制热特性均得到准确模拟,验证了所建模型的可靠性。     

Simulation model of the thermal performance of a natural convection-type solar tunnel dryer

The basic objective of this paper is to develop a comprehensive simulation model of the thermal performance of solar tunnel dryer. The model is useful in system design as it is sensitive to the design parameters of air collector and dryer (like, length, radius, tunnel tilt, etc.). It is also useful in determining the drying behaviour of high-moisture products (vegetables, fruits, etc.) as well as low-moisture products (barely, wheat, etc.). The performance of the dryer has been estimated for a natural convection mode flow. A transient one-dimensional model was developed for the dryer and the numerical calculations were made for the climate of Delhi. It is observed that a large quantity of barley about 2135 kg can be dried in this dryer within two days of operation upto an equilibrium moisture content. © 1998 John Wiley & Sons Ltd.     

节能环保型热泵干燥装置

介绍一种具有回热循环的闭路式热泵干燥装置,其除效率高,能量利用率高,且封闭循环,是较理想的节能,环保型干燥装置。     

水源热泵系统的仿真与控制

为了优化水源热泵的供热水系统的控制达到节能目的,将系统分为若干部件用MATLAB进行数学建模和仿真,并且根据仿真结果设计了模糊控制器。结果证明系统能够较好的跟随入户热水负荷的变化,比原来节省了大量的电能。     

Energy analysis of hazelnut drying system‐assisted heat pump

In this experimental study, a proportional integral derivative (PID) controlled heat pump dryer was designed and manufactured. Heat pump dryer was tested drying of hazelnut and energy analyses were made. Drying air temperatures were changed as 50,45 and 40°C in the drying system. Drying air velocities were changed as 0.25 m s^?1 for 50°C, 0.32 m s^?1 for 45°C and 0.38 m s^?1 for 40°C. Heating coefficient of performance of whole system (COP_ws) of the heat pump dryer was calculated as 1.70 for 50°C, 1.58 for 45°C and 1.40 for 40°C drying air temperatures. Energy utilization ratio changed between 24 and 65% for 50°C, 17 and 63% for 45°C and 14 and 43% for 40°C drying air temperatures in the heat pump dryer. Copyright © 2008 John Wiley & Sons, Ltd.     

风冷热泵冬季运行模拟与理论计算

建立了风冷热泵冬季运行状态下基于气液分相的集中参数模型。在模型中不仅对蒸发器干工况和结露工况作了数学描述,同时还分析了结霜过程中霜层密度和厚度变化对机组性能的影响,基于这一模型。选择某种热泵进行了计算,得到了这种上机组在不同温湿度和进出水温度下机组的能效比和结霜性能。     

Heat pump use in milk pasteurization: an energy analysis

This study investigates the applicability of heat pumps to milk pasteurization for cheese production and to compare the results with classical pasteurization systems. The experiments are conducted in a liquid‐to‐liquid vapour compression heat pump system and a milk‐to‐milk plate heat exchanger is used as an economizer. The experiments are also conducted in a double jacket boiler system and a plate pasteurization system, which are classical milk pasteurization systems. The results for the three systems are compared and the advantages/disadvantages of using heat pump for milk pasteurization instead of classical systems are determined. It is found that the heat pump consumes less energy than the other two classical systems. Copyright © 2004 John Wiley & Sons, Ltd.     

一种电热固体蓄热装置蓄热过程的数值模拟

本文对10kW电热固体蓄热装置的蓄热过程进行了数值模拟,在将蓄热固体颗粒和粒子间的空气看作均相介质的假设基础上,建立了蓄热过程中蓄热体内径向传热模型,根据初始条件和边界条件进行了数值计算,分析了误差产生可能原因,并利用有效导热系数分析了数值解和实验结果之间的误差。