Effects of system control strategies on startup characteristics of R290 room air conditioners

A thermal network model for hydrocarbon heat pump systems: A coupling analysis of configuration, working condition, and refrigeration distribution

“…A control strategy based on the optimization of the profiles of electronic expansion valves has been proposed to control the migration of refrigerants and lubrication, thereby reducing the probability of oil blockages [33]. Owing to their low charge levels, under low-temperature heating, R290 HPs can also suffer from subatmospheric suction pressures during cold startups [34]. Although several specific solutions have been developed to resolve these failures, the internal mechanisms of these abnormal phenomena have not been studied comprehensively.…”

Experimental Study on the Feasibility of Quick Startup of Instant Heat Pump Water Heaters Based on Active Control of Heat Sink Flow Step

“…Compared with hot water boilers, electric water heaters, and gas water heaters, heat pump water heaters (HPWHs) have been promoted and applied in many countries by virtue of their energy-saving and high-efficiency advantages in hot water production, and have been also the focus of attention of many scholars [6][7][8][9]. Drastic state changes occur during startup, which can affect the startup time, safety (negative-and high-pressure operation), and energy efficiency of heat pump and air-conditioning systems, where the startup time is primarily connected to thermal comfort and user satisfaction [10][11][12][13][14]. The startup time of the instant heat pump water heater (IHPWH) is directly related to the ability to quickly produce domestic hot water that meets the required temperature.…”