Abstract
The chapter is focused on technology of heat and moisture regeneration for ventilation systems. In the first sub-division recent progress in adsorptive technologies for air dehumidification, heating and conditioning is analyzed. In the next sub-divisions results of original researches of authors on adsorptive heat and moisture regeneration are given. The design of adsorptive heat-moisture regenerator for ventilation systems is shown. Its operation and the results of field tests are described. The technology of regeneration of low-potential heat and moisture by composite sorbent ‘silica gel – sodium sulphate' is suggested. Experimental plots of temperature, absolute and relative humidity at the inlet and the outlet of the apparatus and between cassettes with the composite are given. Correlation of flows switch-over time, airflow rate and temperature drop is stated. The relationships temperature efficiency factor vs. dimensionless temperature drop and moisture efficiency factor vs. absolute humidity dimensionless drop are derived with fair accuracy for engineering calculation. Ability of purposeful modification of the above-mentioned characteristics within broad ranges by changing the half-cycle time, the size of the granules of the adsorbent and its amount is revealed. The mathematical model and algorithm for determining the basic parameters of adsorptive regenerator operating processes are developed. The proposed algorithm involves calculating the volume of air passed through the layer of adsorptive heat-storage material, the concentration of water in the airflow at the outlet of the regenerator, the adsorption, the heat of adsorption, the final temperature of the cold air, the air temperature after mixing the cold air from the street and the warm air in the room at the warm end of the regenerator during inflow, calculation of the final concentration of water in the flow at the cold end of the regenerator, the volume of air passing through the layer of heat-accumulating material, adsorption and heat of adsorption, the final temperature of the air at the cold end of the regenerator, the air temperature after mixing of the cold air from the street and the warm air from the room at the cold end of regenerator during outflow, determining the temperature efficiency coefficient, summarized adsorption and maximal adsorption time. The correlation of air temperatures near the warm and cold end of the regenerator, as well as the temperature efficiency factors calculated according to the proposed algorithm and obtained by experimental way is confirmed. The mathematical modeling of the processes of operation of adsorption regenerators based on composites ‘silica gel – sodium sulphate' and ‘sodium acetate' in the conditions of the typical ventilation system of residential premises is carried out. The dependences of the temperature efficiency factor vs. the time of switching air flows and the velocity of air flow, as well as the temperatures of external and internal air under stationary conditions are shown. An optimal composition of composite adsorbents is stated to be 20% of silica gel and 80% of salt, that is, sodium sulphate or sodium acetate. Due to higher value of maximal adsorption composite ‘silica gel – Na2SO4' is shown to be required in half as much as compared with ‘silica gel – CH3COONa'. The results of the research can be used in the development of energy-efficient ventilation systems and devices for residential and warehouse premises.