Experimental study of heat and mass transfer characteristics in a cross-flow heating tower

Huang, Shifang; Lv, Zhenyu; Liang, Caihua; Zhang, Xiaosong

doi:10.1016/j.ijrefrig.2017.02.020

Cited by 33 publications

(14 citation statements)

References 23 publications

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“…The correlation expressions of those two coefficients are expressed as functions of the solution mass flow flux, , and air mass flow flux, [28] : ℎ = 4.7600 0.4289 0.8678 ,…”

Section: Expansion Valvementioning

confidence: 99%

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Performance comparison of a heating tower heat pump and an air-source heat pump: A comprehensive modeling and simulation study

Huang

Zuo

Lu³

et al. 2019

Energy Conversion and Management

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The heating tower heat pump (HTHP) is proposed as an alternative to the conventional air-source heat pump (ASHP). To investigate the performance improvements of the HTHP over the ASHP, a comprehensive comparison between the two systems was carried out based on a simulation study. Physics-based models for the ASHP and HTHP were developed. The performance of the ASHP under frosting conditions was corrected with a newly developed frosting map, and the regeneration penalization was considered for the HTHP. Based on the models and corrections, hourly simulations were carried out in an office building in Nanjing, China. The results show that the average energy efficiency of the HTHP in summer is 23.1% higher than that of the ASHP due to the water-cooled approach adopted by the HTHP. In winter, the HTHP achieves an increase of 7.4% in efficiency due to the frost free and energy storage characteristics. While the initial cost of the HTHP is 1.2% higher than that of the ASHP, the HTHP can still save 9.7% cost in a 10-year period because of its lower power consumption.

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“…The correlation expressions of those two coefficients are expressed as functions of the solution mass flow flux, , and air mass flow flux, [28] : ℎ = 4.7600 0.4289 0.8678 ,…”

Section: Expansion Valvementioning

confidence: 99%

“…where is the pressure of local atmospheric, which is 101.325 kPa in this study. To simplify the calculation, the vapor pressure of solution is often expressed as equivalent humidity ratio [28] :…”

Section: Refrigerant Air Water and Solutionmentioning

confidence: 99%

Performance comparison of a heating tower heat pump and an air-source heat pump: A comprehensive modeling and simulation study

Huang

Zuo

Lu³

et al. 2019

Energy Conversion and Management

Self Cite

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“…Then, the correlation formula of the heat transfer coefficient is acquired by regression. Huang et al (2017) constructed an experimental system with glycol solution as the working medium. The heat transfer coefficient is studied without consideration of the Lewis law.…”

Section: Introductionmentioning

confidence: 99%

Effects of the operation parameters of a closed-type heating tower on the performance of heating tower heat pump system

Feng

Zhao

et al. 2020

Energy Exploration & Exploitation

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The ventilator of the heating tower and the circulating pump of the anti-freeze solution are the main electrical equipment of a heating tower heat pump system, besides the compressor. By controlling the working frequencies of the ventilator of the heating tower and circulating pump of the anti-freeze solution, the effects of the operation parameters of a closed-type heating tower on its heat absorption and the performance of heating tower heat pump system were investigated under winter heat conditions. The results indicated that reducing the frequency of the circulating pump for the anti-freeze solution leads to a decrease in the temperature of the outlet evaporator of the anti-freezing solution and an increased temperature difference between the anti-freeze solution flowing into and out of the heating tower; meanwhile, excessively high and low anti-freeze flow rates lead to reduced heat absorption of the closed-type heating tower. The coefficient of performance fluctuates slightly if the frequency of circulating pump is above 20 Hz, but a slight drop in coefficient of performance is observed when the frequency is less than 15 Hz. The system energy efficiency ratio tends to increase as the frequency of circulating pump is reduced, although a substantial reduction occurs at 10 Hz. Furthermore, a reduced ventilator frequency decreases the temperatures of the anti-freeze solution at the inlet and outlet of the heating tower and the temperature difference, hindering the heat absorption of the heating tower. With reductions in the ventilator frequency, the coefficient of performance exhibits an initial increase followed by subsequent decreases, while the system energy efficiency ratio showed continual increases until the ventilator frequency dropped to 10 Hz. When the ventilator frequency or circulating pump frequency drops to 15 Hz and 10 Hz, the evaporation temperature of the heat pump unit decreases, resulting in an excessively exhaust temperature, which is not favorable for the safe operation of the system.

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“…Chillers with cooling towers are the most widely used systems for cooling supply in large commercial buildings due to their high energy efficiency [1]. Inspired by the heat rejection process in a standard cooling tower, previous research proposed a reversibly-used cooling tower, named as heating tower [2,3]. This tower can be used to transfer heat from ambient air to water or solution with low temperature.…”

Section: Introductionmentioning

confidence: 99%

Model-based optimal operation of heating tower heat pump systems

Huang

Zhang

et al. 2019

Building and Environment

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In current applications of heating tower heat pumps (HTHPs), the systems tend to run with constant speed or fixed set points, which can be inefficient under varying weather data and building loads. To address this issue, this study proposes a model-based optimal operation of the HTHPs to achieve energy savings in both cooling and heating modes. Firstly, a physics-based model for an existing HTHP system was developed. Then, artificial neural network (ANN) models were developed and trained with vast amount of operational data generated by the physics-based model. The ANN models were found to be highly accurate (average relative error less than 1%) and computationally efficient (about 300 times faster than the physics-based model). After that, three optimal approaches were proposed to minimize the total energy consumption of the HTHP system. Approach 1 optimizes the load distribution between different heat pump units. Approach 2 optimizes the speed of fans and pumps by fixed approach and range of the condenser water (or evaporator solution). Approach 3 optimizes both the load distribution and the speed of fans and pumps. The optimization is implemented by using the ANN models, proposed approaches, and a genetic algorithm via a case study. The results show that the energy savings in the cooling season are 2.7%, 11.4%, and 14.8% by the three approaches, respectively. In the heating season, the energy savings of the three approaches are 1.6%, -1.4%, and 4.7%, respectively. Moreover, the thermodynamic performance in typical days was analyzed to investigate how energy savings could be achieved.

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Experimental study of heat and mass transfer characteristics in a cross-flow heating tower

Cited by 33 publications

References 23 publications

Performance comparison of a heating tower heat pump and an air-source heat pump: A comprehensive modeling and simulation study

Performance comparison of a heating tower heat pump and an air-source heat pump: A comprehensive modeling and simulation study

Effects of the operation parameters of a closed-type heating tower on the performance of heating tower heat pump system

Model-based optimal operation of heating tower heat pump systems

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