Analytical model based performance evaluation, sizing and coupling flow optimization of liquid desiccant run-around membrane energy exchanger systems

Abstract 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%.

[1]  Stanley A. Mumma,et al.  Practical thermal performance correlations for molecular sieve and silica gel loaded enthalpy wheels , 2005 .

[2]  Li-Zhi Zhang.  An Analytical Solution to Heat and Mass Transfer in Hollow Fiber Membrane Contactors for Liquid Desiccant Air Dehumidification , 2011 .

[3]  Carey J. Simonson,et al.  Application of neural networks to predict the steady state performance of a Run-Around Membrane Energy Exchanger , 2012 .

[4]  Fu Xiao,et al.  Control performance of a dedicated outdoor air system adopting liquid desiccant dehumidification , 2011 .

[5]  Carey J. Simonson,et al.  Performance testing of a counter-cross-flow run-around membrane energy exchanger (RAMEE) system for HVAC applications , 2010 .

[6]  R. Besant,et al.  Transient behavior of run-around heat and moisture exchanger system. Part І: Model formulation and verification , 2009 .

[7]  Haisheng Fan,et al.  Performance of a Run-Around System for HVAC Heat and Moisture Transfer Applications Using Cross-Flow Plate Exchangers Coupled with Aqueous Lithium Bromide , 2006 .

[8]  C. J. Simonson,et al.  Part-load performance of energy wheels: Part 1 -- Wheel speed control , 2000 .

[9]  Robert E. Wilson,et al.  Fundamentals of momentum, heat, and mass transfer , 1969 .

[10]  H. Hemingson.  The impacts of outdoor air conditions and non-uniform exchanger channels on a run around membrane energy exchanger , 2010 .

[11]  Carey J. Simonson,et al.  The elastic and moisture transfer properties of polyethylene and polypropylene membranes for use in liquid-to-air energy exchangers , 2007 .

[12]  C. Oliet,et al.  Numerical simulation of dehumidifying fin-and-tube heat exchangers: Semi-analytical modelling and experimental comparison , 2007 .

[13]  R. Besant,et al.  Numerical model and effectiveness correlations for a run-around heat recovery system with combined counter and cross flow exchangers , 2009 .

[14]  R. Besant,et al.  Energy wheel effectiveness: part I—development of dimensionless groups , 1999 .

[15]  Carey J. Simonson,et al.  Air-to-air exchangers , 2003 .

[16]  Frank P. Incropera,et al.  Fundamentals of Heat and Mass Transfer , 1981 .

[17]  R. W. Besant,et al.  Air-to-Air Energy Recovery , 2000 .

[18]  Mohammad Rasouli,et al.  Applicability and optimum control strategy of energy recovery ventilators in different climatic conditions , 2010 .

[19]  D. Goswami,et al.  Study of an aqueous lithium chloride desiccant system: air dehumidification and desiccant regeneration , 2002 .

[20]  R. Besant,et al.  Steady-state performance of a run-around membrane energy exchanger (RAMEE) for a range of outdoor air conditions , 2011 .

[21]  Cai-Hang Liang,et al.  Performance analysis of a direct expansion air dehumidification system combined with membrane-based total heat recovery , 2010 .

[22]  K. Y. Qu,et al.  Experimental study on mass transfer performances of cross flow dehumidifier using liquid desiccant , 2006 .

[23]  Li-Zhi Zhang.  An analytical solution for heat mass transfer in a hollow fiber membrane based air-to-air heat mass exchanger , 2010 .

[24]  Jianlei Niu,et al.  Energy requirements for conditioning fresh air and the long-term savings with a membrane-based energy recovery ventilator in Hong Kong , 2001 .

[25]  Ruzhu Wang,et al.  Performance of energy recovery ventilator with various weathers and temperature set-points , 2007 .

[26]  Stanley A. Mumma,et al.  Dedicated Outdoor Air-Dual Wheel System Control Requirements , 2001 .