Performance of a gas engine driven heat pump for hot water supply systems E. Elgendy a, * , J. Schmidt a , A. Khalil b , M. Fatouh c a Institute of Fluid Dynamics and Thermodynamics, Faculty of Process and System Engineering, Otto-von-Guericke University, Universitätsplatz 2, D-39106 Magdeburg, Germany b Mechanical Power Engineering Department, Faculty of Engineering, Cairo University, Giza 12316, Egypt c Mechanical Power Engineering Department, Faculty of Engineering at El-Mattaria, Helwan University, Masaken El-Helmia P.O., Cairo 11718, Egypt article info Article history: Received 29 October 2010 Received in revised form 13 January 2011 Accepted 13 February 2011 Available online 15 March 2011 Keywords: Gas engine heat pump Heating mode R410A Water heating Primary energy ratio Heat recovery abstract The present work aimed at evaluating the experimental performance of a gas engine heat pump for hot water supply. In order to achieve this objective, a test facility was developed and experiments were performed over a wide range of ambient air temperature (10.9e25.3  C), condenser water inlet temperature (33e49  C) and at two engine speeds (1300 and 1750 rpm). Performance characteristics of the gas engine heat pump were characterized by water outlet temperatures , total heating capacity and primary energy ratio. The reported results revealed that hot water outlet temperature between 35 and 70  C can be obtained over the considered range of the operating parameters. Also, total heating capacity and gas engine heat recovery decrease by 9.3 and 27.7%, respectively, while gas engine energy consumption increases by 17.5% when the condenser water inlet temperature changes from 33 to 49  C. Total heating capacity, gas engine heat recovery and gas engine energy consumption at ambient air temperature of 25.3  C are higher than those at ambient air temperature of 10.9  C by about 10.9, 6.3 and 1.5% respectively. Moreover, system primary energy ratio decreases by 15.3% when the engine speed changes from 1300 to 1750 rpm. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction In Germany, space and process heating sector requires around 60% of the total annual final energy consumption, covered by nearly 80% with imported fossil fuel, which is responsible for more than 50% of the total, energy-related CO 2 -emissions [1]. Improvement of energy efficiency utilization of the systems, which cover this sector, represents basis of integration of the environmental dimension into energy policy. Heat pumps (HPs) are believed to offer the best prospects for attaining this goal in a wide variety of appropriate heating applications [2e4]. HPs can be used to heat water for either domestic hot water requirements or space heating applications. According to primary energy source, HPs can be classified as elec- tric driven heat pumps (EHPs) and gas engine driven heat pumps (GEHPs). GEHP usually consists of a vapor compression heat pump with an open compressor driven by a gas engine instead of an electric motor. Nowadays, GEHP has been paid more attention due to its advantage of reducing the energy consumption in the heating process. Another two distinguished advantages of the GEHP are (1) the ability to recover the waste heat released by the engine cylinder jacket and exhaust gas and (2) the easy modulation of the engine speed by adjusting the gas supply. Therefore, GEHP has a better performance than electric driven heat pump (EHP), especially in heating mode [5]. Performance characteristics of the GEHP used in heating mode are evaluated by many investigators using theoretical modeling [5e7] and experimental approach [8,9]. Regarding to theoretical modeling of the GEHP, Zhang et al. [5] analyzed the effect of both ambient air temperature and engine speed on the heating perfor- mance of the GEHP based on steady state model. The results proved that, the engine speed had a remarkable effect on both the engine and the heat pump, but the ambient temperature had a little influence on the engine performance. Yang et al. [6] reported an intelligent control simulation model for the GEHP system in heat- ing mode to predict its dynamic characteristics. The results showed that the model was very effective in analyzing the effect of the control system. The steady state accuracy of the intelligent control scheme was higher than that of the fuzzy controller. Sanaye and Chahartaghi [7] developed a theoretical model to predict the performance of the GEHP under different operating modes. Comparison of the simulation results with the experimental data showed that error percentages of suction pressure, discharge pressure, fuel consumption and coefficient of performance are 3.4%, 4%, 6.7% and 7.2%, respectively, in cooling mode and 3.7%, 5.4%, 8.1% and 7.8%, respectively, in heating mode. * Corresponding author. Tel.: þ49 391 67 12558; fax: þ49 391 67 12762. E-mail address: essam.elgendy@st.ovgu.de (E. Elgendy). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy 0360-5442/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.energy.2011.02.030 Energy 36 (2011) 2883e2889