Mesoporous MCM-48 silica was synthesized by templating method and the structure of particles was characterized by XRD, TEM and N 2 adsorption techniques. The surface modification of particles in order for introducing into PSF matrix was performed by dimethyldichlorosilane (DMDCS) silylation agent. SEM images of as-synthesized and modified MCM-48/PSF MMMs indicate that in the modified MCM-48 silica particles adhered well to the PSF matrix and that the synthesized MMMs were defect free. The incorporation of MCM-48 particles in to the PSF matrix and also surface coating of these MMMs by polydimethylsiloxane (PDMS) were performed. The quality of surface coating was investigated by SEM images and permeability tests. For all gases tested (N 2 , CO 2 , CH 4 and O 2 ), the permeabilities increased in proportion to the weight percent of MCM-48 present in the film and the calculated CO 2 /CH 4 and O 2 / N 2 selectivities of PDMS coated membranes showed enhancement in ideal and actual selectivities both.

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Specific enthalpy of desired conditioned air (at 18 °C and 55 % RH) HPHX Heat pipe heat exchanger HVAC Heating, ventilation, and air conditioninġ m Mass flow rate of air passing through the condenseṙ m min Minimum of mass flow rates between air streams in pre-cooling and reheating sections q act Actual heat transfer rate q max Maximum heat transfer rate RH Relative humidity RH e,i Relative humidity of inlet air to the HPHX evaporator S e Energy saving in evaporator section S c Energy saving in condenser section S t Total energy saving T c,i Temperature of inlet air to the HPHX condenser T C,d Temperature of desired outlet air from the AC system (at 9 °C and 100 % RH) T c,o Temperature of outlet air from the HPHX condenser T e,i Temperature of inlet air to the HPHX evaporator T e,o Temperature of outlet air from the HPHX evaporator ε Effectiveness of HPHX δ Uncertainty