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13.4.4 Refrigerant management and servicing In high ambient regions, the average condensing temperatures are higher than in other regions and vapour-liquid heat transferring takes less proportion of the total condensing heat load due to the higher condensing temperatures. Average higher compression ratios due to larger temperature lift results in higher compressor power and potential shorter compressor life. The viscosity of the oil decreases and the insulation of the motor is affected. This coupled with the long working hours leads to higher risk of compressor breakdown and other failures (Li, 2014). At HAT conditions, there is an increased possibility for systems to be contaminated with moisture, which requires special service skills and the need to improve service practices. This enforces the importance of education and training for the operators and technicians handling systems. The risks associated with flammability, while not limited to HAT countries, are accentuated due to the higher refrigerant charge associated with systems operating at higher temperatures. HAT countries need special requirements for maintenance and repair including but not limited to some extra components and controls like leak sensors and liquid injection to reduce the discharge temperature. For the same surface area to be conditioned, the average capacity of units installed in HAT regions is larger than those in more temperate climates with larger refrigerant charge. The larger charge and the low maintenance associated with some of the countries in those regions might result in higher direct emissions. 13.4.5 Technological capabilities of the local industry The PRAHA project (see section 5 in this chapter) concluded that the research and development (R&D) personnel at OEMs in some of the HAT countries have diverse skills and design capabilities but need to acquire the knowledge of designing for low-GWP, flammable alternative refrigerants with the assistance of the technology providers. A full product redesign is needed for most of the products with a comprehensive process of design analysis, optimization and validation of results. (PRAHA, 2016). Some manufacturers have started experimenting with low-GWP alternatives and designing for high ambient temperatures and designers are acquiring the maturity in designing and optimising products using those alternatives. On the other hand, research programmes at local institutes and centers in HAT countries related to assessing future refrigerants and technologies have not been implemented yet. A second phase of the PRAHA project is working with global associations and research centres to support the process of decision-making related to the acceptance and promotion of low-GWP alternatives. Building the local design capabilities empowers local institutes to play key roles in assessing the local technological needs related to the promotion of low-GWP alternatives through the development of a comprehensive risk assessment model (PRAHA, 2017). 13.5 Limitations and design considerations The objective of this section is to summarise the performance of the various HCFC-22 options for high ambient air conditioning applications. The governing thermodynamic properties and principles result in a declining capacity and efficiency as the heat-rejection (refrigerant condensing) temperature increases. This is valid for all refrigerants including HCFC-22; however, some of the HCFC-22 replacements exhibit greater degradation in capacity and efficiency than HCFC-22 under high ambient temperature conditions. 2018 TOC Refrigeration, A/C and Heat Pumps Assessment Report 259PDF Image | Heat Pumps Technical Options
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