ES precept 6

Pagina 1

Precept 6: Vapor-compression refrigeration cycle Mechanical Engineering - Energy Systems Authors: •Group xx: xxxxx xxxxx (xxxxxxxx), F abio Santoro (xxxxxxxx) Lecturer:Prof. Stef ano Consonni T eaching Assistants:Riccardo Cremona, Hamidreza Heydari and Nima Razmjoo Academic year:2025-2026 Contents Description 2 1 Plant scheme,p-handT-sdiagrams 3 2 Thermodynamic properties 4 3 Compressor volumetric fluid rate and displacement 6 4 Thermal power rejected by condenser 6 5 Fan and compressor electrical power 6 6 Coefficient of performances: cycle and plant 7 7 Double-throttling refrigeration configuration 8 8 Single vs double throttling comparison 14 References 14 1 Energy Systems - Report Precept 6 - Group xx Description The topic of this precept is the design of a refrigeration system for fresh food storage. The system consists in a vapour-compressor (reciprocating single action volumetric), one evaporator and one lami- nation valve. The working fluid isR134a, the other general data is collected in Table 1. The condenser is a compact tube with fin heat exchanger as represented in Figure 1 and in Table 2 we collected the data of the heat exchanger an the ambient air conditions. Extra data will be provided in each request. Table 1: Design parameter of the refrigeration cycle Symbol Value Unit Description ˙QREF 18 kW Refrigeration power (evaporation) TEV A -4 ◦C Evaporation temperature ∆TSH 2 ◦C Superheating in the evaporator ∆TSC 3 ◦C Condensate subcooling temperature ηis 70 % Compressor isoetropic efficiency ηem 88 % Electro-mechanical efficiency of the compressor driver ηvol 90 % Compressor volumetric efficiency n2970 rpm Compressor rotating speed Figure 1: Condenser: heat exchanger layout Table 2: Design parameter of the tube and fin heat exchanger and ambient air…