Belal Dawoud

Experimental study on the kinetics of water vapor sorption on selective water sorbents, silica gel and alumina under typical operating conditions of sorption heat pumps

Abstract A selective water sorbent (SWS) is a composite material consisting of a porous host matrix and a hygroscopic substance (commonly an inorganic salt) impregnated into its pores. This work presents an experimental investigation for the kinetics of water vapor sorption on two host materials; namely mesoporous silica gel and alumina in comparison with the two composites SWS-1L and SWS-1A formed by impregnating these two host matrices with CaCl 2 . Moreover, the kinetics of water vapor sorption on microporous silica gel have been also investigated. The measurements have been carried out on 3 g samples of loose pellets on an isothermal wall under three different operating conditions of sorption heat pumps. The results obtained evidence a remarkable increase in the differential water loading of both SWS-sorbents over their host materials. However, and due to the increased diffusion resistance to water sorption resulting from the salt impregnation, the kinetics of water sorption into the host matrices is faster than that into the two SWS-composites. Moreover, SWS-1L is found to be faster than SWS-1A in sorbing water vapor. The differential water loading on microporous silica is about twice that on mesoporous silica and alumina, but the sorption kinetics are a little bit slower.

Dynamic modeling of the combined heat and mass transfer during the adsorption/desorption of water vapor into/from a zeolite layer of an adsorption heat pump

This paper presents a one-dimensional model describing the combined heat and mass transfer during the adsorption/desorption of water vapor into/from a zeolite layer in a small-scale adsorption heat pump. The model is utilized to study the dynamics of both adsorption and desorption processes as well as to examine the influence of both the layer thickness and the volume of the vapor phase of the adsorber/desorber heat exchanger on their time requirements. The model equations have been numerically solved using the software packet gPROMS (general PROcess Modeling System) [http://www.psenterprise.com/gPROMS]. The duration of the adsorption process is found to be generally longer than that of the desorption process, depending on the zeolite layer thickness. Reducing the layer thickness by 50% results in a reduction to 25% in the duration of the adsorption process and to about 33% of the desorption process. In order to get reasonable power densities from an adsorption heat pump using zeolite layers, the layer thickness must not exceed 2.5 mm. Moreover, the volume of the vapor phase of the adsorber/desorber heat exchanger has to be minimized, in order to minimize the unavoidable losses of the coefficient of performance of the periodical adsorption heat pump due to the pre-cooling as well as the pre-heating phases.

Adsorption Heat Exchangers

As described in Chap. 1, one of the major adsorber heat exchanger design requirements is the reduction of the ratio between the heat capacity of the adsorber heat exchanger material as well as its heat transfer medium’s holdup and the heat capacity of the applied adsorbent. This results in enhancing the coefficient of performance of the adsorption heat pump and increases the obtainable specific heating or cooling power.

Mechanical Stability of Adsorbent Coatings

An adsorbent material consolidated in form of coating could present poor mechanical stability if a proper binder and/or an optimized binder content are not adopted in the coating formulation. Mechanical stability of the adsorbent coating may be affected by different typologies of mechanical stresses during its lifetime (vibrations, impacts, etc.). For this reason, a single mechanical test is not sufficient to prove completely the overall mechanical stability of the coated layer.

Hydrothermal Stability of Adsorbent Coatings

Hydrothermal aging of zeolites is an irreversible change of adsorbent surface characteristics due to repeated cyclic adsorption and desorption of water resulting in, among others, reduced adsorption capacity and kinetics of adsorption.

Basics of Adsorption Heat Pump Processes

A heat pump process is a thermodynamic process having the main target to pump heat from a heat reservoir at a low temperature (ambient heat source) to a heat sink at a higher temperature (heating net). According to the second law of thermodynamics, this target can only be realized if a driving energy is applied. Contrary to the vapor compression heat pump process, where mechanical work is applied as a driving energy to run the compressor, thermally driven heat pumps (TDHP) make use of heat at a higher temperature (driving heat source), compared to the heat sink temperature, as a driving energy.

Technical and Economical Feasibility of Gas Turbine Inlet Cooling Using Evaporative Fogging System in Two Different Locations in Oman

In this paper gas turbine power boost via inlet air evaporative fogging system is evaluated for power plants of 40 MW power output in two different locations in Sultanate of Oman. The cooling effect is quantified using evaporative cooling degree hour (ECDH) approach. The power output boost based on the month with the highest number of evaporative cooling degree hours reaches as high as 20% for both locations.. This is significant in view of the increased air conditioning load during summer months. It is found that the average net present value (NPV) of installing fogging system in Marmul is

Experimental investigation of an adsorptive thermal energy storage

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Thermodynamic assessment of power requirements and impact of different gas-turbine inlet air cooling techniques at two different locations in Oman

6,182,496. It is also found that the purchase and installation costs are paid back within the first six months of system operation and for later years, annual revenue of over

Adsorbent coatings for heat pumping applications: Verification of hydrothermal and mechanical stabilities

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