A review on the equations of state for the working pairs used in adsorption cooling systems H.Z. Hassan a,n , A.A. Mohamad b , Y. Alyousef c , H.A. Al-Ansary d a Department of Mechanical Engineering, College of Engineering, Alfaisal University, Takhassusi St., PO Box 50927, Riyadh 11533, Saudi Arabia b Mechanical and Manufacturing Engineering, Centre for Energy and Environment, Research and Education, Schulich School of Engineering, University of Calgary, Calgary, AB, Canada c King Abdullaziz City for Science and Technology, Institute of Water and Energy Research, PO Box 6086, Riyadh 11442, Saudi Arabia d Mechanical Engineering Department, The College of Engineering, King Saud University, Riyadh, Saudi Arabia article info Article history: Received 26 February 2014 Received in revised form 28 December 2014 Accepted 6 February 2015 Keywords: Adsorption pair Cooling State equation Adsorption equilibrium abstract Adsorption cooling machines are thermally driven systems. Solar radiation, waste energy, as well as geothermal energy can be used to power these systems. Theoretical study and simulation work of adsorption-based cooling systems require the knowledge about the adsorption pair characteristics and capacities at different conditions of working pressures and temperatures. This information is obtained from the adsorbate–adsorbent equation of state. Various models and formulas represent the adsorption pair equation of state for different combinations of adsorbate and adsorbent can be found in the literature. Furthermore, these state equations include some coefficients which are determined experi- mentally for each combination of the adsorption pair. The present work introduces a review of various adsorption equations of state which have been adopted by different researchers in their study. Moreover, the corresponding experimentally evaluated coefficients, which are found in the literature, for each model and for a variety of working pairs are reported as well. & 2015 Elsevier Ltd. All rights reserved. Contents 1. Introduction ........................................................................................................ 600 2. Characteristics of the adsorbent–adsorbate pairs........................................................................... 602 3. Adsorption dynamic equilibrium and kinetics ............................................................................. 602 4. Adsorption equilibrium models ........................................................................................ 603 4.1. Dubinin equations ............................................................................................. 603 4.2. Langmuir equation............................................................................................. 604 4.3. Freundlich equation ............................................................................................ 604 4.4. Toth equation................................................................................................. 604 5. Activated carbon state equations ....................................................................................... 604 6. Silica gel state equations .............................................................................................. 606 7. Zeolite state equations ............................................................................................... 607 8. Conclusion ......................................................................................................... 608 Acknowledgements ...................................................................................................... 608 References ............................................................................................................. 608 1. Introduction Sorption phenomenon has been known for long time and is increasingly used in many applications including separation, purification, and thermally driven cold production technologies [1]. The term “sorption” refers to both absorption and adsorption Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/rser Renewable and Sustainable Energy Reviews http://dx.doi.org/10.1016/j.rser.2015.02.008 1364-0321/& 2015 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ966 1215 7790; fax: þ966 12157751. E-mail addresses: hzahmed@alfaisal.edu, zoheir_hasan@yahoo.com (H.Z. Hassan). Renewable and Sustainable Energy Reviews 45 (2015) 600–609