Advanced Method of Variable Refrigerant Flow (VRF) Systems Designing to Forecast Onsite Operation—Part 2: Phenomenological Simulation to Recoup Refrigeration Energy

Abstract

This paper focuses on the application of speed-regulated compressors (SRCs) to cover changeable heat loads with high efficiency in conventional air conditioning systems (ACS) as well as in the more advanced variable refrigerant flow (VRF)-type outdoor and indoor ACS. In reality, an SRC is an oversized compressor, although it can operate efficiently at part loads. The higher the level of regulated loads (LRL) of the SRC, the more the compressor is oversized. It is preferable to reduce the size of the SRC by covering the peak loads and recouping the excessive refrigeration energy reserved at decreased actual loads within the range of regulated loads. Therefore, the range of changeable loads is chosen as the object to be narrowed by using the reserved refrigeration capacity. Thus, the general fundamental approach of dividing the overall heat load range of the ACS into the ranges with changeable and unchangeable loads, as previously developed by the authors, is applied for the range of primary changeable loads. Due to this innovative step, the principle of two-stage outdoor air conditioning according to changeable and unchangeable loads, also proposed by the authors, has been extended over the range of primary changeable loads to reduce the level of refrigeration capacity regulation and SRC size. To realize this, part of the changeable load range is offset by the reserved refrigeration capacity, leading to a reduction in the changeable load range and the SRC size by approximately 20% for temperate climatic conditions.

Research of hydrodynamic processes in the flow part of a low-flow thermopressor

“…A general way to increase the efficiency of power plants is to utilize the exhaust heat [1][2][3] and cool the working fluid [4] to provide favorable conditions for their efficient operation by application of waste heat recovery chillers [5,6] or electrically driven vapor compression refrigeration machines as in air conditioning system [7,8]. The air is a general working fluid in the majority of the power plants based on combustion engines, in particular, gas turbines [9,10], internal combustion engines [11,12], as well as in air conditioning systems as subsystems which provide processing (cooling) engine intake air or as autonomous systems in stationary [13][14][15] and transport application [16,17]. The various types of heat exchangers and feeding circuits are used for cooling air [18][19][20].…”

Increasing the Efficiency of Turbine Inlet Air Cooling in Climatic Conditions of China through Rational Designing—Part 1: A Case Study for Subtropical Climate: General Approaches and Criteria

“…In contrast to comfort (space) air conditioning [71,72] with annual refrigeration energy production in response to its consumption as a criterion [73,74], in engine cyclic air cooling, the annual fuel reduction is applied as criterion [57,75] to determine the rational capacities to achieve maximum output.…”

Innovative approaches and modified criteria to improve a thermodynamic efficiency of trigeneration plants

“…There are many methods applied to optimize the heat loads on exhaust heat utilization and air-cooling systems [45,46] in order to mееt actual loading [47,48], gain a maximum output [49,50] and improve operation performance of engines [51,52]. They focus to enhance output of engines due to sucked air cooling at varying actual ambient temperatures [53,54].…”