Performance enhancement of vapor recompression heat pump M.A. Waheed a , A.O. Oni a,⇑ , S.B. Adejuyigbe a , B.A. Adewumi b , D.A. Fadare c a Department of Mechanical Engineering, Federal University of Agriculture, Abeokuta, P.M.B. 2240 Ogun State, Nigeria b Department of Agricultural Engineering, Federal University of Agriculture, Abeokuta, P.M.B. 2240 Ogun State, Nigeria c Department of Mechanical Engineering, University of Ibadan, P.M.B. 1 Ibadan, Nigeria highlights  We developed various models for the enhancement of vapor recompression heat pump.  Utilization of hot process or utility streams was considered in the models.  Efforts were made to minimize heat losses and heat pump size.  The thermoeconomic and environmental performances of the models were investigated.  The applications of the models will reduce total annual cost and emission rate. article info Article history: Received 19 July 2013 Received in revised form 4 September 2013 Accepted 14 September 2013 Keywords: Heat pump Thermoeconomic Environmental Energy savings Performance abstract The vapor recompression heat pump (VRHP) has the potentials of reducing the energy requirements of fractionating close-boiling mixtures. It improves the quality of low grade heat with the aid of heat pump to provide heat input to the reboiler. However, this technology does not utilize heat efficiently resulting in appreciable heat loss in the condenser. In this study, enhanced VRHP models were developed to reduce the heat loss and heat pump size. The strategies adopted rely on reducing the heat differential across the heat pump by utilizing external and utility streams, and process stream within the system. The thermo- economic and environmental performances of the developed models were compared with the base case VRHP and the conventional distillation process. The results showed that the developed models yielded considerable energy savings. Considering the present trend of short process modification payback time, the use of an external process stream is recommended as the most preferred option to boost the plant performance. However, in situation where such streams are not available within the plant premises or uneconomical due to their influence in the chosen exchanger network, the utilization of process streams within the system will be a much more attractive alternative option. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The conventional distillation system is widely use in the petro- leum and chemical industries for the separation of fluid mixtures. This system of separation is highly energy intensive [1–5]. Reports have shown that about 40–60% of the energy used by the chemical and refining industry is for the separation of products by distilla- tion [6–8]. The continuous rise in energy cost, the increasing public concern and the international environmental regulations makes it imperative for the process industries to look for ways to reduce en- ergy demands. For this reason, any research thrust that will reduce energy consumption, environmental burden and satisfies product requirement in distillation processes is of high demand. The quest to improve efficiency and lessen environmental im- pact associated with distillation processes is an on-going concern. Various techniques, such as heat integration, heat pumps, thermal couplings and others have been employed to achieve energy reductions [9–11]. One of the most promising strategies has been the introduction of heat pumps which was first proposed in the mid-1970s [12–14]. Today, different types of assisted heat pump distillation systems exist and have found practical applications in the industries. The most commonly used are the absorption heat pump (AHP) and mechanical heat pump (MHP) [15,16]. The MHP is categorized into three types, the vapor recompression heat pump (VRHP), bottom flash heat pump (BFHP) and closed cycle heat pump (CCHP) [17]. Of the aforementioned types, the VRHP has gained more recognition due to its outstanding benefits [10,17]. This technology pressurizes vapor of a low grade heat to a higher grade by using mechanical power and, then the pressur- ized vapor provides a heating effect when condensing. However, 0306-2619/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.apenergy.2013.09.024 ⇑ Corresponding author. Tel.: +234 803 4072 399. E-mail address: fem2day@yahoo.com (A.O. Oni). Applied Energy 114 (2014) 69–79 Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy