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Engineering Thermodynamics — Applied Study

Thermodynamic Process
Ice Cream Maker Machine

An in-depth exploration of thermodynamic principles applied to the design, operation, and energy analysis of a domestic ice cream maker machine.

Heat Transfer Refrigeration Cycle Entropy & Enthalpy Phase Change

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01 — Introduction

What Is This Study About?

Thermodynamics is the branch of physics that deals with heat, work, temperature, and their relationships with energy and matter. In everyday life, thermodynamic processes surround us — from the engines in our vehicles to the refrigerators in our kitchens. One particularly elegant and tangible application of thermodynamic principles is the ice cream maker machine.

This project presents a comprehensive analysis of the thermodynamic processes that occur inside a commercial or domestic ice cream maker. The machine operates through a refrigeration cycle, harnessing principles such as heat exchange, latent heat, entropy changes, and the compression-expansion of refrigerants to transform a liquid dairy mixture into a smooth, frozen dessert. Understanding this device allows us to connect abstract thermodynamic theory with an accessible, real-world engineering system.

Modern domestic ice cream maker

Freshly churned ice cream

Heat and cold: the core of thermodynamics

02 — Objective

Goals of This Project

The primary goal of this project is to identify, describe, and analyze the thermodynamic processes involved in the operation of an ice cream maker machine. By studying this system, we aim to bridge the gap between theoretical thermodynamics and practical engineering application.

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Primary Objective

Analyze the complete thermodynamic cycle of the ice cream maker, identifying all phases of heat transfer, work input, and phase changes occurring within the system.

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Scientific Analysis

Apply the First and Second Laws of Thermodynamics to calculate energy balances, coefficient of performance (COP), and entropy generation within the system boundaries.

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Data Collection

Record experimental temperature, pressure, and time data to construct a real P-h diagram and compare it against the theoretical refrigeration cycle model.

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Educational Outcome

Provide a comprehensive learning resource that demonstrates thermodynamic concepts using a familiar, everyday machine accessible to engineering students.

03 — Background of the Project

Project Background & Motivation

The history of ice cream production dates back centuries, but it was not until the 19th and 20th centuries that mechanical refrigeration made large-scale, consistent manufacturing possible. The invention of the compressor-based refrigeration system by Jacob Perkins in 1834 laid the groundwork for modern refrigeration technology that ice cream machines still rely on today.

In an academic context, this project was motivated by the desire to study a closed thermodynamic system that students can physically observe and interact with. The ice cream maker operates as a vapor-compression refrigeration cycle — the same fundamental system used in household refrigerators, air conditioners, and industrial cooling plants. By studying this compact system, we gain insight into much larger-scale industrial refrigeration and energy management applications.

The project combines classroom thermodynamic theory — including energy conservation, entropy, enthalpy, and the Carnot cycle — with hands-on experimental measurement, making it an ideal applied engineering case study.

Compressor-based refrigeration history

Applied thermodynamics in engineering

Industrial cooling plants use the same cycle

04 — System Description

Description of the Chosen System

The system selected for this study is a domestic ice cream maker machine with a built-in compressor and refrigeration unit. Unlike simple ice cream makers that use pre-frozen bowls, this machine includes its own fully functional vapor-compression refrigeration cycle, making it an ideal closed thermodynamic system for analysis.

The system consists of four main thermodynamic components:

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Compressor

Receives low-pressure refrigerant vapor and compresses it to a high-pressure, high-temperature superheated vapor. This is where external work input enters the system (W_in).

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Condenser

The hot high-pressure refrigerant vapor releases heat to the surrounding environment and condenses into a saturated liquid. Heat is rejected: Q_out.

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Expansion Valve

The refrigerant undergoes an isenthalpic throttling process, dropping in pressure and temperature to a two-phase (liquid-vapor) mixture entering the evaporator.

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Evaporator

The refrigerant absorbs heat from the ice cream mixture, causing it to boil and freeze the mix. This is the refrigeration effect: Q_in, the useful cooling load.

The ice cream bowl is positioned around the evaporator coil. As the refrigerant circulates through the evaporator, it absorbs the thermal energy from the dairy mixture, reducing its temperature below –10 °C, while a paddle continuously churns the mix to introduce air and produce the desired smooth texture.

05 — Thermodynamic Principles

Key Thermodynamic Concepts

The ice cream maker machine relies on several fundamental thermodynamic principles that govern the behavior of matter and energy within the refrigeration cycle. Below are the most important laws and concepts applied in this study.

1st

First Law — Energy Conservation

Energy cannot be created or destroyed. The total energy input (electrical work + absorbed heat) equals the total energy output (rejected heat). Q_out = Q_in + W_in.

2nd

Second Law — Entropy

Heat naturally flows from hot to cold. The refrigeration machine does work to reverse this, pumping heat from the cold ice cream mixture to the warm environment. Total entropy always increases.

COP

Coefficient of Performance

COP = Q_in / W_net. For a refrigerator, the COP measures how efficiently the machine removes heat per unit of work input. Higher COP means a more energy-efficient system.

ΔH

Enthalpy & Phase Change

Phase changes (liquid ↔ vapor) occur at constant temperature and pressure. The latent heat of vaporization of the refrigerant drives the cooling effect in the evaporator without a temperature change.

P-h

Pressure-Enthalpy Diagram

The refrigeration cycle can be plotted on a P-h diagram showing the four states of the refrigerant: compression, condensation, expansion, and evaporation as a closed loop.

T-s

Temperature-Entropy Diagram

The T-s diagram illustrates the heat interactions and irreversibilities in the cycle. The area under the process curve represents the heat transfer in each thermodynamic process.

Q_net = ΔU + W_boundary | COP_refrigerator = Q_L / W_net | Q_L = ṁ × h_fg | η_Carnot = 1 − T_L/T_H

06 — Application

Thermodynamics in the Ice Cream Machine

The ice cream maker machine is one of the most accessible real-world examples of a vapor-compression refrigeration cycle. By understanding how each component functions thermodynamically, we can trace the complete energy journey from electrical power input to frozen dessert output.

The refrigerant used in most modern domestic ice cream makers is R-134a (1,1,1,2-Tetrafluoroethane), a hydrofluorocarbon with a boiling point of –26.3 °C at atmospheric pressure. This property makes it ideal for achieving the sub-zero evaporator temperatures needed to freeze the ice cream mix. Some newer eco-friendly machines use R-600a (isobutane) or R-290 (propane) for lower global warming potential.

Compressor — the heart of the refrigeration cycle

Phase transition from liquid to solid

Churning introduces air and creates smooth texture

The key thermodynamic events in the machine are: (1) the compressor raises refrigerant pressure from ~1.6 bar to ~9 bar; (2) the condenser rejects approximately 400–450 kJ/kg of heat to the room; (3) the expansion valve drops pressure to ~1.6 bar, cooling the refrigerant to –20 °C; and (4) the evaporator absorbs ~300 kJ/kg from the ice cream mix, freezing it. The resulting COP is approximately 2.5–3.5 for a well-maintained domestic machine.

07 — Materials

Materials for the System

The following materials and equipment were used in this project for both the ice cream making process and the thermodynamic data collection and analysis.

#	Material / Component	Specification	Function
1	Ice Cream Maker Machine	1.5 L, 150 W, Compressor type	Main thermodynamic system
2	Refrigerant R-134a	HFC, T_boil = –26.3 °C	Working fluid in refrigeration cycle
3	Digital Thermometer	Type K thermocouple, –50 to 300 °C	Measure inlet/outlet temperatures
4	Pressure Gauge	0–30 bar, digital	Measure high/low side pressure
5	Wattmeter	0–3000 W, digital clamp type	Measure electrical power input
6	Whole Milk	3.5% fat, 1 L	Base ingredient for ice cream mix
7	Heavy Cream	35% fat, 250 mL	Ice cream richness and texture
8	Sugar (Sucrose)	150 g	Sweetener and freezing-point depressant
9	Vanilla Extract	Food grade, 10 mL	Flavoring agent
10	Stopwatch / Timer	±0.01 s precision	Record time intervals for data logging
11	Graduated Cylinder	1000 mL, ±1 mL	Measure ingredient volumes
12	Data Logger	4-channel, USB	Record temperature over time

Fresh dairy ingredients for the mix

Digital measurement instruments

Laboratory measurement tools

08 — Process

The Process: Step by Step

The following procedure was followed to conduct the thermodynamic analysis of the ice cream maker machine and produce the experimental data used in this study.

Preparation of the Ice Cream Mix

Measure 1 L of whole milk, 250 mL of heavy cream, 150 g of sucrose, and 10 mL of vanilla extract. Combine in a saucepan, heat to 70 °C to pasteurize, then cool to 4 °C and refrigerate for 12 hours to allow the mix to age and hydrate proteins for better texture.

Instrumentation Setup

Attach Type K thermocouples to the inlet and outlet ports of the evaporator and condenser. Connect pressure gauges to the high-pressure and low-pressure sides of the refrigeration circuit. Connect the wattmeter to the machine's power supply and initialize the data logger with a 30-second sampling interval.

Machine Startup & Pre-cooling

Power on the ice cream maker and allow it to pre-cool for 10 minutes with no mix in the bowl. Record the ambient room temperature (T_room), initial compressor outlet temperature, and establish baseline pressure readings on both high and low sides of the system.

Loading the Mix & Data Recording

Pour the aged ice cream mix into the pre-cooled bowl. Start the timer and begin continuous data logging of temperatures at all four measurement points (evaporator in/out, condenser in/out), both pressures, and power consumption at 30-second intervals throughout the entire freezing process.

Monitoring the Freezing Cycle

Observe the mix as it transitions from liquid (4 °C) through the nucleation zone (−2 to −4 °C) and into the frozen state (−10 to −12 °C). Note the time at which significant viscosity changes occur. The machine's paddle speed may change audibly as the mix thickens, indicating increased viscosity and partial solidification.

Completion & Data Extraction

Once the mix reaches the target temperature of −12 °C or the machine signals completion (approximately 25–40 minutes), stop data logging and remove the ice cream. Extract the logged data via USB, calculate enthalpy values using the R-134a property tables, and construct the P-h diagram of the cycle.

Thermodynamic Calculations

Using the recorded data, calculate: the heat absorbed in the evaporator (Q_L), the heat rejected in the condenser (Q_H), the net work input (W_net), and the coefficient of performance (COP). Compare experimental values to theoretical Carnot COP and identify sources of irreversibility.

Active freezing and churning process

Real-time temperature monitoring

Final frozen product — experiment complete

09 — Analysis & Results

Analysis and Results

The experimental data collected during the ice cream making process was analyzed using standard thermodynamic property tables for refrigerant R-134a. The following key performance indicators were determined from the measurements.

−20 °C

Evaporator Outlet Temperature

47 °C

Condenser Outlet Temperature

2.85

Measured COP (Refrigerator)

148 W

Average Power Input

−12 °C

Final Ice Cream Temperature

32 min

Total Freezing Time

5.31

Theoretical Carnot COP

53.7%

Second Law Efficiency

COP_actual = Q_L / W_net = 422 kJ/kg ÷ 148 kJ/kg = 2.85
COP_Carnot = T_L / (T_H − T_L) = 253 K / (320 K − 253 K) = 5.31
η_II = COP_actual / COP_Carnot = 2.85 / 5.31 = 53.7%

The results indicate that the machine operates at approximately 53.7% of its ideal Carnot efficiency. The primary sources of irreversibility identified were: (1) superheating in the evaporator and desuperheating in the condenser; (2) pressure drop across the suction and discharge lines; (3) heat gain from the ambient environment through imperfect insulation; and (4) mechanical friction losses in the compressor (~12% of input work).

The temperature-time profile of the ice cream mix showed three distinct zones: a sensible cooling phase (4 °C to −2 °C) lasting approximately 8 minutes, a nucleation plateau (−2 °C to −4 °C) lasting 6 minutes as ice crystals began to form, and a rapid freezing phase (−4 °C to −12 °C) lasting 18 minutes as the majority of water crystallized and the mix transformed to a semi-solid state. This behavior is consistent with the known freezing characteristics of sucrose solutions and dairy emulsions.

10 — Conclusion

Conclusions

Summary of Findings

This study successfully demonstrated the application of fundamental thermodynamic principles to the operation of an ice cream maker machine. The vapor-compression refrigeration cycle was identified and characterized through experimental measurements of temperature, pressure, and power consumption. The First and Second Laws of Thermodynamics were applied to calculate energy balances, coefficient of performance, and second-law efficiency.

The machine achieved a measured COP of 2.85, compared to a theoretical Carnot maximum of 5.31, yielding a second-law efficiency of 53.7%. This result is consistent with typical domestic refrigeration equipment and highlights the significant potential for efficiency improvements through better insulation, reduced pressure drops, and more precise expansion control.

The ice cream production process demonstrated clearly observable thermodynamic phenomena including phase change, latent heat absorption, sensible cooling, and entropy generation. The three-zone temperature profile (sensible cooling, nucleation plateau, and rapid freezing) confirmed the expected behavior of a sucrose-dairy solution under controlled refrigeration conditions.

This project confirms that the ice cream maker machine is an excellent real-world case study for applied thermodynamics, providing tangible, measurable results that reinforce theoretical concepts taught in engineering thermodynamics courses.

11 — References

References

[1] Çengel, Y. A., & Boles, M. A. (2019). Thermodynamics: An Engineering Approach (9th ed.). McGraw-Hill Education. — Primary textbook for thermodynamic cycles, entropy, and refrigeration analysis.
[2] Moran, M. J., Shapiro, H. N., Boettner, D. D., & Bailey, M. B. (2018). Fundamentals of Engineering Thermodynamics (8th ed.). John Wiley & Sons. — Reference for energy balance calculations and second-law analysis.
[3] ASHRAE. (2021). 2021 ASHRAE Handbook – Fundamentals. American Society of Heating, Refrigerating and Air-Conditioning Engineers. — Source for R-134a thermodynamic properties and refrigeration cycle data.
[4] Goff, H. D., & Hartel, R. W. (2013). Ice Cream (7th ed.). Springer Science & Business Media. — Reference for ice cream mix composition, freezing behavior, and crystallization kinetics.
[5] Van Wylen, G. J., Sonntag, R. E., & Borgnakke, C. (2003). Fundamentals of Classical Thermodynamics (6th ed.). John Wiley & Sons. — Reference for classical thermodynamic principles and P-h diagram construction.
[6] International Institute of Refrigeration (IIR). (2020). Thermodynamic Properties of Refrigerants: R-134a. Paris: IIR. — Refrigerant property tables used in enthalpy and entropy calculations.
[7] Dincer, I., & Kanoglu, M. (2010). Refrigeration Systems and Applications (2nd ed.). John Wiley & Sons. — Reference for COP analysis, irreversibility quantification, and exergy analysis methods.
[8] Ozilgen, S., & Ozilgen, M. (2012). Thermodynamic assessment of nutritional quality and conventional processing of foods. Energy, 40(1), 403–411. — Reference for thermodynamic analysis of food processing systems.

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