ABSTRACT The present chapter deals with the studies carried out in recent years at the University of Genoa, Italy, concerning the use of membrane contactors for air dehumidification and their integration into air-conditioning plants in order to improve the performances of heat pumps, thereby saving energy. In the first part of this chapter (sections 2-6) experimental and numerical studies regarding air dehumidification by means of hydrophobic membrane contactors and LiCl desiccant solutions are reported. Desiccant-membrane systems offer several potential benefits: large working membrane area per unit volume; no carryover of liquid-phase droplets; no pollution of the liquid phase by atmospheric dust; good dehumidification efficiency, and potential high-efficiency control of the quality of the handled air. Specifically, experimental tests on a plane-plate cross-flow membrane contactor prototype, made up of composite PTFE membranes fixed to PP supports, are described. A FORTRAN computer code able to study the behaviour of the contactor has been developed. Theoretical analysis involves mass and energy equations for both air and liquid desiccant. Moreover, heat and vapour mass fluxes through the membrane have been analysed. The agreement between theoretical predictions and the experimental data has been discussed. The possibility of using membrane contactors in air-conditioning systems is discussed in the second part of the chapter (sections 7-10). Specifically, the performances of a hybrid air-conditioning system in which a vapour-compression inverse cycle is integrated with an air dehumidification system working with membrane contactors and a hygroscopic solution have been investigated. This plant may be a valid alternative to traditional summertime air-conditioning systems, in which the air is cooled to below its dew-point temperature and subsequently reheated. The advantage of the hybrid system lies in the fact that the refrigeration device operates at a higher evaporation temperature than that of a traditional system, in which dehumidification is achieved through condensation. The proposed hybrid system involves simultaneously cooling and dehumidifying the air conveyed to the conditioned space in an air-solution membrane contactor. An LiCl solution is cooled by means of a vapour-compression inverse cycle using the refrigerant KLEA 410A. The solution is regenerated in another membrane contactor by exploiting the heat exchanged by the condenser. A SIMULINK calculation programme was specially designed in order to simulate the system under examination in steady-state conditions. The performances of the system were analysed on varying the most significant operating parameters and were compared with those of a traditional air-conditioning plant in a typical case-study of summertime air-conditioning. The results of the simulations revealed significant energy savings, which, in particular operating conditions, may exceed 50%.

How to improve the performances of heat pumps in air conditioning plants using membrane contactor dehumidification/regeneration systems

BERGERO, STEFANO;CHIARI, ANNA
2013

Abstract

ABSTRACT The present chapter deals with the studies carried out in recent years at the University of Genoa, Italy, concerning the use of membrane contactors for air dehumidification and their integration into air-conditioning plants in order to improve the performances of heat pumps, thereby saving energy. In the first part of this chapter (sections 2-6) experimental and numerical studies regarding air dehumidification by means of hydrophobic membrane contactors and LiCl desiccant solutions are reported. Desiccant-membrane systems offer several potential benefits: large working membrane area per unit volume; no carryover of liquid-phase droplets; no pollution of the liquid phase by atmospheric dust; good dehumidification efficiency, and potential high-efficiency control of the quality of the handled air. Specifically, experimental tests on a plane-plate cross-flow membrane contactor prototype, made up of composite PTFE membranes fixed to PP supports, are described. A FORTRAN computer code able to study the behaviour of the contactor has been developed. Theoretical analysis involves mass and energy equations for both air and liquid desiccant. Moreover, heat and vapour mass fluxes through the membrane have been analysed. The agreement between theoretical predictions and the experimental data has been discussed. The possibility of using membrane contactors in air-conditioning systems is discussed in the second part of the chapter (sections 7-10). Specifically, the performances of a hybrid air-conditioning system in which a vapour-compression inverse cycle is integrated with an air dehumidification system working with membrane contactors and a hygroscopic solution have been investigated. This plant may be a valid alternative to traditional summertime air-conditioning systems, in which the air is cooled to below its dew-point temperature and subsequently reheated. The advantage of the hybrid system lies in the fact that the refrigeration device operates at a higher evaporation temperature than that of a traditional system, in which dehumidification is achieved through condensation. The proposed hybrid system involves simultaneously cooling and dehumidifying the air conveyed to the conditioned space in an air-solution membrane contactor. An LiCl solution is cooled by means of a vapour-compression inverse cycle using the refrigerant KLEA 410A. The solution is regenerated in another membrane contactor by exploiting the heat exchanged by the condenser. A SIMULINK calculation programme was specially designed in order to simulate the system under examination in steady-state conditions. The performances of the system were analysed on varying the most significant operating parameters and were compared with those of a traditional air-conditioning plant in a typical case-study of summertime air-conditioning. The results of the simulations revealed significant energy savings, which, in particular operating conditions, may exceed 50%.
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11567/505519
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 1
  • ???jsp.display-item.citation.isi??? ND
social impact