Laboratory Evaluation and Field Tests of Replacements for R22 and R502

Per Lundqvist Dr., Lars Herbe M.Sc, The Royal Institute ofTechnology, Dept. of Energy Technology, S-100 44, Stockholm, Sweden Fax: +46 8 20 30 07 Tel: +46 8 790 74 52 Email: [email protected] There are several important issues when dealing with new refrigerants in a retrofit situation. This paper is however restricted to system performance and a discussion of methods suitable to determine the performance. The cooling capacity and COP are strongly dependent on the system design (type of heat exchangers, compressors, receivers etc.). The difference between two refrigerants in the same system is usually much smaller than two different systems operating with the same refrigerant. The studied systems are therefore both plate-type heat exchanger systems with small charge and larger chillers with shell and tube type heat exchangers. The paper deals with some of the problems that may occur in the latter type of equipment. Experiences of methods and limitations for field evaluation are given. The differences with pure and a zeotropic refrigerants are discussed with respect to this problem. The importance of collecting refrigerant samples for gas chromatography is stressed. Introduction The retrofit activities in Sweden have, so far, been focused on refrigeration and heat pump plants operating with Rl2, R500 and R502. The schedule for phase-out is described in figure I. The timetable means a real challenge for the Swedish refrigeration industry and, above all, a hard pressure on the users. The retrofit ofR12 plants is now believed to have reached 50% of the refrigerant charge! The alternative here is Rl34a. The introduction ofR404A for R502 plants has met minor competition from the zeotropic alternatives R407A and B. ASHRAE Primary Type of Stop for Stop for Stop for use Share of the Number replacement refrigerant import or refill total refrigerant new charge in installations Sweden Ill R12 R134a CFC 1111995 1111998 1112000 32% R500 R134a CFC 1111995 1111998 1112000 6% R502 R404A~ CFC 1111995 1/11998 1112000 12% R22 R407C HCFC 1111998 1112002 50% Table 1. Schedule for the phase-out of ozone depleting refrigerants in Sweden One aim of this paper is to describe, and compare, the methods for evaluation of alternative refrigerants that have been used at our department in cooperation with the Swedish refrigeration industry. We believe that the work described here has been an important part of the "knowledge formation" required for the retrofit activities on the field. Parallel with the work described here is a work dealing with the practical retrofit methods coupled to the chemical environment in the refrigeration circuit after, for example, a conversion from Rl2 with mineral oil to Rl34a with ester oil (this work is presented in another paper at the conference). The work is mainly sponsored by NUTEK as a joint research program called "Alternative Refrigerants". Parts ofthe work reported here are also sponsored in-house by several individual companies involved in the field. Some of the work have been performed by the students at Applied thermodynamics and Refrigeration, KTH, as master of science projects. The program "Alternative Refrigerants" involves several other projects such as natural refrigerants, heat transfer studies etc. 1 Other refrigerants such as Rll, RI3, Rl3bl etc have been omitted 2 Some competition from R407 A and B