Energy and Buildings 62 (2013) 248–257 Contents lists available at SciVerse ScienceDirect Energy and Buildings j ourna l ho me pa g e: www.elsevier.com/locate/enbuild Analytical model based performance evaluation, sizing and coupling flow optimization of liquid desiccant run-around membrane energy exchanger systems Gaoming Ge ∗ , Davood Ghadiri Moghaddam, Ramin Namvar, Carey J. Simonson, Robert W. Besant Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, S7N 5A9, Canada a r t i c l e i n f o Article history: Received 26 October 2012 Received in revised form 22 January 2013 Accepted 9 March 2013 Keywords: Run-around membrane energy exchanger Analytical model Effectiveness Optimization Unbalanced airflow a b s t r a c t A run-around membrane energy exchanger (RAMEE) is a novel energy recovery system which can avoid carryover of desiccant solution while transferring both heat and moisture between non-adjacent supply and exhaust air streams. In this study, an analytical model for a flat-plate counter-cross-flow liquid- to-air membrane energy exchanger (LAMEE) is compared with experimental test results and numerical simulations for a single LAMEE and a RAMEE system under various operating conditions. Agreements are obtained among the analytical, experimental and numerical results. The effectiveness of a RAMEE system under balanced and unbalanced airflow conditions is evaluated by using the analytical model. Optimization studies for exchanger size and solution flow rate in RAMEE systems are investigated. Results show that RAMEE systems with equal-sized supply and exhaust exchangers can achieve the highest effectiveness in most conditions for both balanced and unbalanced airflow. Optimization control of the solution flow rate can enhance annual energy recovery rate up to 7%. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Energy recovery ventilators (ERVs) are important because they can reduce energy consumption, reduce capacity/size of cool- ing/heating source and air handling equipment, and enhance dehumidification control robustness for building heating, ventilat- ing and air-conditioning (HVAC) systems [1,2]. Extensive research has been conducted for different types of ERVs, e.g.: energy wheels [3–5], permeable membrane plate exchangers [6,7], twin-tower enthalpy recovery loops [8]. ERVs can precondition the outdoor ventilation air by transferring both heat and moisture between exhaust air and outdoor air. Nevertheless, the currently available ERVs encounter some challenges for applications. For instance, the requirement of adjacent supply and exhaust air streams imposes higher ducting costs and larger ceiling space for ducts in new or retrofit buildings, while the possibility of cross-contamination of supply air streams in energy wheels and plate exchangers or carryover of desiccant solution in twin tower loops limits their applications for some types of buildings, such as health care facil- ities. The run-around membrane energy exchanger (RAMEE) is a novel energy recovery system, which consists of two or more sepa- rate flat-plate liquid-to-air membrane energy exchangers (LAMEE) ∗ Corresponding author. Tel.: +1 306 966 5476; fax: +1 306 966 5427. E-mail addresses: gag827@mail.usask.ca, gegaoming@gmail.com (G. Ge). comprised of water-vapor permeable membranes and coupled with a closed loop of aqueous salt solution flow, i.e. lithium- chloride (LiCl) or magnesium-chloride (MgCl 2 ) aqueous solution [1,9]. These LAMEE devices are capable of transferring both heat and moisture between non-adjacent exhaust and outdoor air streams in a RAMEE system and avoid the problems of current ERVs. Different types of RAMEE systems, with cross-flow [10–12], counter-flow [13] and counter-cross-flow [9,14] exchanger con- figurations have been investigated. Numerical simulations and experimental tests on the steady-state and transient heat and mass transfer behaviors of these RAMEE systems were conducted. It is found that the counter-cross-flow configuration is convenient for manufacturing and can achieve higher effectiveness [8,15] than the cross-flow exchanger with the same membrane area. Although a numerical model for counter-cross-flow RAMEE systems has been developed and it is accurate to predict the system energy perfor- mance, it is too computationally time consuming to be used for system design and is not practical for performance optimization for applications [1]. Hence, a simple correlation or model that can pre- dict or characterize the energy performance of a single LAMEE and RAMEE systems would be very useful. Akbari et al. [16] developed neural network (NN) models to predict the steady-state perfor- mance of a RAMEE system. These NN models are computationally fast and easy to use for system design and optimization, but the training and validation processes are complex. The NN models require large amounts of data to train the models to get accurate 0378-7788/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.enbuild.2013.03.017