Development of a modular zeolite-water heat pump

On the Effect of Grain Size on the Kinetics of Water Vapor Adsorption and Desorption into/from Loose Pellets of FAM-Z02 under a Typical Operating Condition of Adsorption Heat Pumps

“…Rapid increase of τ 0.8 and τ 0.9 and the corresponding reduction in the specific evaporator cooling and condenser heating capacities for pellets larger than 1.4 to1.6 mm select this size as the upper limit for applying in adsorption heat pumps with loose adsorbent layers. It is worthy to mention here that the obtained specific evaporator cooling or condenser heating capacities are valid only as a maximum for the designs of Lang et al, (1999), Stricker (2003) and Dawoud et al (2007) who made use of one single pellet layer between the fins of finned tube adsorber heat exchangers. For the common packed bed heat exchanger design, these results are not valid and further investigations are required.…”

“…One of the methodologies to apply zeolite on adsorber heat exchangers is to locate it in form of loose pellets between the fins of finned-tube heat exchangers (Lang et al, 1999;Stricker, 2003;Núñez et al, 2005;Dawoud et al, 2007). This methodology offers the maximum adsorbent surface area for mass transfer.…”

“…This implies that an adsorber heat exchanger with the lowest possible grain size would be the most effective design. As the main idea of applying loose pellets was to allow only one layer of adsorbent grains between each two successive fins (Lang et al, 1999;Stricker, 2003;Dawoud et al, 2007), the lowest possible grain size would require an infinite number of fins. This indeed increases the thermal capacity ratio between the adsorber heat exchanger and the adsorbent leading to a poor heat pump performance (Westerfeld, 1996).…”

Basics of Adsorption Heat Pump Processes

“…1.11, the maximum achievable uptake is reduced to (x Ads at state point I of the real cycle). In the same time, the minimum uptake x min of the ideal cycle is increased to x Des in the [60,61] real cycle (state point III). Accordingly, the maximum evaporator cooling effect of the real cycle can be expressed by Eq.…”

A new methodology of studying the dynamics of water sorption/desorption under real operating conditions of adsorption heat pumps: Modelling of coupled heat and mass transfer in a single adsorbent grain

“…The characteristic time s of isobaric adsorption (desorption) was measured for one layer of loose grains of 1.4-1.6 mm in size for different boundary conditions of adsorption heat pumps. This approach allows a direct measurement of the temporal evolution of average water uptake under conditions, which closely simulate the scenario of temperature jump or drop in real adsorption heat pumps and refrigerators with a layer of loose grains [2,3]. Such jump is a driving force of water desorption/adsorption during isobaric stages of the cycle of these units.…”