Modeling and Optimization of a CoolingTower-Assisted Heat Pump System

Xiaoqing Wei, Nianping Li, Jinqing Peng, Jianlin Cheng, Jinhua Hu and Meng Wang
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Xiaoqing Wei: College of Civil Engineering, Hunan University, Changsha 410082, China
Nianping Li: College of Civil Engineering, Hunan University, Changsha 410082, China
Jinqing Peng: College of Civil Engineering, Hunan University, Changsha 410082, China
Jianlin Cheng: College of Civil Engineering, Hunan University, Changsha 410082, China
Jinhua Hu: College of Civil Engineering, Hunan University, Changsha 410082, China
Meng Wang: College of Civil Engineering, Hunan University, Changsha 410082, China

Energies, 2017, vol. 10, issue 5, 1-18

Abstract: To minimize the total energy consumption of a cooling tower-assisted heat pump (CTAHP) system in cooling mode, a model-based control strategy with hybrid optimization algorithm for the system is presented in this paper. An existing experimental device, which mainly contains a closed wet cooling tower with counter flow construction, a condenser water loop and a water-to-water heat pump unit, is selected as the study object. Theoretical and empirical models of the related components and their interactions are developed. The four variables, viz. desired cooling load, ambient wet-bulb temperature, temperature and flow rate of chilled water at the inlet of evaporator, are set to independent variables. The system power consumption can be minimized by optimizing input powers of cooling tower fan, spray water pump, condenser water pump and compressor. The optimal input power of spray water pump is determined experimentally. Implemented on MATLAB, a hybrid optimization algorithm, which combines the Limited memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm with the greedy diffusion search (GDS) algorithm, is incorporated to solve the minimization problem of energy consumption and predict the system’s optimal set-points under quasi-steady-state conditions. The integrated simulation tool is validated against experimental data. The results obtained demonstrate the proposed operation strategy is reliable, and can save energy by 20.8% as compared to an uncontrolled system under certain testing conditions.

Keywords: cooling tower-assisted heat pump; theoretical and empirical models; energy saving; hybrid optimization algorithm (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2017
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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