Effects of Flowrate and Temperature on System Efficiency 

Background

The goal was to explore how variations in inlet water temperature and refrigerant flowrate impact refrigeration system efficiency, and to apply these findings to the design of a refrigeration system for cooling fudge in a small-scale confectionery operation. This work connected thermodynamic theory with practical industrial applications in food processing, environmental control, and chemical manufacturing.

Action

Our project integrated experimental testing, thermodynamic modeling, and applied design analysis:

System Construction and Operation:

Designed and operated a closed-loop refrigeration system using R-427A, a non-toxic, non-flammable hydrofluorocarbon blend chosen as an environmentally safer alternative to R-22.

Key components included a compressor, condenser, expansion valves (throttle and orifice types), evaporator coil, and suction accumulator, with system monitoring via wattmeter and temperature probes.

Experimental Methodology:

Varied inlet water temperature to determine its influence on COP and U.

Adjusted refrigerant flowrate under both open and closed circuit conditions.

Collected and analyzed data using temperature and flow sensors, energy balances, and efficiency calculations.

Theoretical Framework:

Applied concepts from the reverse Carnot cycle, Joule-Thomson effect, and convective heat transfer correlations to interpret results.

Equations governing enthalpy change, compressor work, and heat rejection were used to model performance trends.

Design Application – Fudge Cooling System:

Translated lab-scale findings into a practical design for cooling fudge in a Gatlinburg, TN confectionery.

Design Targets: Cool 2 ft × 1 ft × 0.75 in batches of fudge from 238°F to 70°F.

Calculated Load: 1.20 refrigeration tons, requiring 1.58 HP compressor power.

Evaluated feasibility, size, and efficiency of system components based on experimental performance data.

Result

The study demonstrated key performance relationships:

COP decreased with increasing inlet water temperature, confirming reduced thermodynamic efficiency under higher thermal loads.

Heat transfer coefficient (U) increased as inlet temperature decreased, indicating enhanced cooling potential at lower operating conditions.

Higher refrigerant flowrates improved heat transfer but also raised compressor power demands, requiring optimization for energy efficiency.

The final design provided a technically viable refrigeration system capable of meeting cooling demands for confectionery production with improved energy performance and environmental compliance.

Through this project, I strengthened my skills in thermodynamic modeling, experimental data analysis, heat transfer design, and process optimization, while gaining practical experience in applying core chemical engineering principles to real-world food process design.