OPEN ACCESS
A numerical study on the cooling performance of new air-conditioning systems based on the reversed air cycle is conducted through a specifi cally developed computer code. The main peculiarity of such HVAC systems is the combination of the roles traditionally played separately by the chiller and the air handling unit, as the expanded cool air is directly supplied to the indoor ambient for its environmental control. For any system proposed, simulations have been carried out for a wide variety of psychrometric states of both outdoor air and supply air, and for different effi ciencies of the heat exchangers and the turbomachinery. Among the main results obtained, it is found that for hot and dry climates, as well as for temperate climates, the values of the cooling performance of the most advanced confi gurations are of the same order as those typical for traditional HVAC systems served by vapour-compression refrigerating units.
air-conditioning, innovative integrated systems, numerical simulations, reversed Brayton cycle.
[1] Fantini, L. & Nannei, E., Sull’utilizzazione di un ciclo inverso a gas in macchine ad effetto frigorigeno, prima parte. Il Freddo, 2/91, p. 175, 1991.
[2] Mattarolo, L., Tecnologia del freddo e impatto ambientale. Il Freddo, 6/94, p. 495, 1994.
[3] Lorentzen, G., The use of natural refrigerants: a complete solution to the CFC/HCFC predicament. Int. J. Refrig., 18(3), pp. 190–197, 1995.
[4] Riffat, S.B., Afonso, C.F., Oliveira, A.C. & Reay, D.A., Natural refrigerants for refrigeration and air-conditioning systems. Appl. Therm. Eng., 17(1), pp. 33–42, 1997.
[5] Kruse, H., L’impiego dei fl uidi naturali. Il Freddo, 1/97, p. 41, 1997.
[6] Gigiel, A., De Chauveron, S. & Fitt, P., Air as a replacement for CFC refrigerants. Proposals for the Generation and Use of Refrigeration in the 21st Century, Buenos Aires, Argentina, IIR/IIF edn, pp. 83–92, 1992.
[7] ASHRAE, Air-cycle equipment (Chapter 14). 1988 ASHRAE Handbook: Equipment, ASHRAE: Atlanta, GA, 1988.
[8] Cappelli D’Orazio, M., Cianfrini, C. & Corcione, M., An air-conditioning system based on the reverse Joule-Brayton cycle. Int. J. Heat Technol., 18(2), pp. 91–100, 2000.
[9] Cappelli D’Orazio, M., Cianfrini, C., Corcione, M. & Moncada, G., Developments of reverse open air-cycle systems for air conditioning terrestrial applications. Proc. of the 7th Rehva World Congress Clima 2000, Naples, Italy, 2001.
[10] Pescod, D., A heat exchanger for energy saving in an air conditioning plant. ASHRAE Trans., 85, pp. 238–251, 1979.
[11] Maclaine-Cross, I.L. & Banks, P.J., A general theory of wet surface heat exchangers and its application to regenerative evaporative cooling. J. Heat Transfer, 103, pp. 579–585, 1981.
[12] Dumas, A. & Piva, S., Analisi di scambiatori statici aria-aria con fenomeni di condensazione ed evaporazione. CDA, 3-88, p. 389, 1988.
[13] Dumas, A. & Corradini, E., Presenza di un velo liquido di acqua sulle superfi ci di uno scambiatore aria-aria. CDA, 9-96, p. 1012, 1996.
[14] Corcione, M., A wet surface three-fl uid type heat exchanger for energy recovery in airconditioning plants. Int. J. Heat Technol., 19(1), pp. 85–94, 2001.
[15] Fantini, L. & Nannei, E., Sull’utilizzazione di un ciclo inverso a gas in macchine ad effetto frigorigeno, seconda parte. Il Freddo, 2/91, p. 277, 1991.
[16] Hyland, R.W. & Wexler, A., Formulations of the thermodynamic properties of the saturated phases of H2O from 173.15 K to 473.15 K. ASHRAE Trans., 89, pp. 500–519, 1983.
[17] Smolsky, B.M. & Sergeev, G.T., Heat and mass transfer with liquid evaporation. Int. J. Heat Mass Transfer, 5(11), pp. 1011–1021, 1962.
[18] ASHRAE, Air-to-air energy-recovery equipment (Chapter 34). 1988 ASHRAE Handbook: Equipment, ASHRAE: Atlanta, GA, 1988.
[19] Hausen, H., Darstellung des Warmeuberganges in Rohren durch verallgemeinerte Potenz-beziehungen. Z. VDI, Beihefte Verfahrenstechink, 4, p. 91, 1943.
[20] ASHRAE, Evaporative air-cooling equipment (Chapter 4). 1988 ASHRAE Handbook: Equipment, ASHRAE: Atlanta, GA, 1988.
[21] Cappelli D’Orazio, M., Cianfrini, C., Corcione, M. & Fontana, D.M., Optimal design and energetic performance of double fi nned-tube coil energy-recuperators. Int. J. Heat Technol., 19(1), pp. 11–22, 2001.