[Mechanical Equipment Technology Edition] Daily Question 20170908 – Refrigeration Design

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This post was last edited by YORK Industrial Refrigeration on 2017-9-11 at 10:23. Starting from now, in order to enhance communication among users, a 【Daily Question】 campaign has been launched on the Mechanical Equipment Technology forum; we hope everyone will participate actively to progress and improve together! ! ! Rewards: 3 wealth for active participation, 10-15 wealth for accurate answers. This question is valid for two days; no scoring will be given after that. Question: Which key parameter is primarily used for selecting a refrigeration compressor? Answer: Basic performance parameters of refrigeration compressors I. Actual gas delivery volume (abbreviated as gas volume) Under certain operating conditions, the mass of gas delivered from the suction side to the discharge side per unit of time is referred to as the compressor’s mass gas delivery volume under those conditions, with the unit being … If calculated based on the volume at inhalation, its volumetric flow rate is, with the unit being. II. Volume Efficiency The volume efficiency of a compressor is the ratio of the actual gas volume delivered to the theoretical gas volume that could be delivered. It is used to measure the degree of effective utilization of the cylinder’s working volume in volume-type compressors. III. Cooling Capacity The cooling compressor is an important component of a refrigeration unit; it works in conjunction with other components in the system, such as heat exchangers and throttling devices, to achieve cooling effects. Therefore, its performance needs to be intuitively expressed by the amount of cooling produced per unit of time – namely the cooling capacity, measured in certain units; this is one of the key performance indicators of a refrigeration compressor. IV. Heat rejection The heat rejection is the sum of the compressor’s cooling capacity and the equivalent heat of a portion of the compressor’s input power; it is discharged through the condenser in the system. This parameter is a very important performance indicator for the compressor in heat pump systems ； This is also essential to know when designing the condenser of a refrigeration system. V. Indicated Power and Indicated Efficiency The indicated work consumed per unit time during an actual cycle is the compressor’s indicated power Pi, measured in kW. The indicated efficiency hi of a refrigeration compressor refers to the ratio of the theoretical isentropic cycle work required to compress 1 kg of refrigerant to the actual indicated work of that cycle. It is used to evaluate the degree of completion of the thermodynamic processes within the compressor cylinder or working volume. 6. Shaft Power, Shaft Efficiency, and Mechanical Efficiency The power transmitted from the prime mover to the compressor’s main shaft is referred to as shaft power, denoted as Pe, with units of kW. A portion of this power, namely indicated power Pi, is used directly to carry out the compressor’s working cycle. The other portion, known as friction power Pm, also in kW, is used to overcome the frictional forces associated with the various moving parts within the compressor, as well as to drive auxiliary equipment such as hydraulic pumps for lubrication. 7. Electrical Power and Efficiency The power supplied to the motor is the electrical power consumed by the compressor, denoted as Pel, measured in kW. Electrical efficiency* is the ratio of the power according to the isentropic compression theory to the electrical power, and it is used to assess the degree of efficiency in utilizing the motor’s input power. 8. Performance Coefficient 　To ultimately assess the power efficiency of a refrigeration compressor, the performance coefficient COP is used; it represents the ratio of the cooling capacity of the compressor under certain operating conditions to the power consumed. ================================ Event Promotion: Petrochemical Zone – “Creative Ideas for Energy Saving” event (the second phase is in full swing) http://bbs.hcbbs.com/thread-1666758-1-1.html (Source: Haichuan Chemical Industry Forum) 2017 Coal Chemical Industry Event – “My Technical Upgrades” http://bbs.hcbbs.com/thread-1786290-1-1.html (Source: Haichuan Chemical Industry Forum)