Internal irreversibility in a water heating solar flat plate collector D.K. Mahanta, Samir Kumar Saha * Department of Mechanical Engineering, Jadavpur University, Calcutta 700 032, India Received 7 August 2000; received in revised form 27 March 2001; accepted 9 October 2001 Abstract In this paper, a study to describe irreversibility in a water heating solar flat plate collector is conducted. The collector is visualized as a heat exchanger, and the study concentrates on minimizing the inter- nal contributions of irreversibility. The analysis is supported by data obtained from ASHRAE based ex- periments on a solar flat plate collector. The objective of this work is to demonstrate the thermodynamic trade-off in the design and operational parameters in a solar flat plate collector of a specific design ap- plication. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Solar collector; Thermodynamic optimization; Entropy; Irreversibility minimization 1. Introduction Irreversibility as a general criterion for estimating and minimizing the usable energy wasted in various thermal systems is widely accepted. A water heating solar flat plate collector is such a thermal system in which the process of collection of solar thermal radiation and its subsequent delivery to a working fluid is associated with both internal and external irreversibilities. The aim of this work is to minimize the internal irreversibilities through minimization of the entropy generation rate. This would provide the most efficient use of energy that is available. It is assumed that the sun-collector and collector-ambient irreversibilities, i.e. the external ir- reversibilities, are fixed or can be assessed [1]. Moreover, the difference between the local tem- peratureofthenon-isothermalcollectorandthebulktemperatureofthefluidisassumedconstant overthelengthofthecollector[2,3].Thefocusisthenconcentratedonminimizationoftheinternal Energy Conversion and Management 43 (2002) 2425–2435 www.elsevier.com/locate/enconman * Corresponding author. Fax: +91-33-472-5823. E-mail address: samirk@cal2.vsnl.net.in (S.K. Saha). 0196-8904/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII:S0196-8904(01)00177-7