The document outlines a senior design project to design, build, and test an optimized refrigeration system using a binary mixture of refrigerants. A team was formed to research various binary refrigerant mixtures to replace traditional single refrigerants and maximize the coefficient of performance (COP) of a domestic refrigerator. The team selected R-125 and R-152a as the binary mixture based on properties like enthalpy and safety. The project will involve building a refrigerator prototype, experimentally determining the optimal mass fraction mixture, and testing to verify the analytical optimization results.

1. MEM-491: Senior Design Fall 2014
Project #25: Binary Refrigerant Refrigerator
Advisor: Bakhtier Farouk
Team Members:
Samuel Beccaria
Mathew Smith
Xiaoyi Zhu
Abhinav Duggal
Friday, December 5, 2014

2. Presentation Outline
➢Problem Statement
○Binary Refrigeration
○Design Problem
■Mixture Optimization
■Prototype Construction and Validation
○Binary Refrigerant Properties
➢Background and Motivation
○New Refrigeration Fluids
➢Stakeholders, Needs, and Specifications
➢Design Methods
○Design Description
➢Design Concepts and Description
○Constraints and Engineering Standards
○Optimization Theory
○Binary Refrigeration Cycle
➢ Context and Impact Analysis
○Environmental Impact Analysis
○Social Impact Analysis
○Ethical Analysis
○Economic Analysis
➢Project Management and Future Work
➢Conclusions and Acknowledgements

3. Problem Statement
Design, build and test an optimized
refrigeration system using a binary
mixture of refrigerants

4. Binary Refrigerant Refrigerators
➢Refrigerant mixtures may lead to better Coefficient of Performance (COP)
➢Refrigerant mixtures could potentially be made to minimize the
environmental harm their individual refrigerant components would create
while still preserving optimal thermophysical properties
➢In this design project, we are evaluating various binary refrigerant
mixtures for possible use in a domestic refrigerator
➢Both azeotropic and non-azeotropic mixtures are being evaluated

5. Design Problem: Mixture Optimization
➢The binary mixture for this project is to be composed of two
pure environmentally safe refrigerants that are acceptable for
domestic use and are not banned by the Montreal Protocol.
➢The task for this project is to optimize the mass fractions of the
individual (pure) fluid components to achieve the highest COP in
a given refrigeration system.
➢A rigorous constrained optimization algorithm will be used to
determine the mixture fractions of the chosen pair of
refrigerants to maximize the COP of the refrigerator

6. Design Problem: Mixture Optimization
➢ COP equation
➢ Saturated enthalpy equations
➢ Saturated pressure equation
➢ Raoult’s Law
➢ Enthalpy of compression
➢ Dalton’s Law

7. Design Problem: Prototype construction
and validation
➢A domestic refrigerator (working with a single refrigerant)
will be procured and the performance will be evaluated
➢The original single refrigerant will be replaced by the
optimum combination of the binary mixture of refrigerants
➢The performance of the refrigerator with the binary
refrigerant system will be tested and evaluated

8. Binary Mixtures

9. Properties of Non-azeotropic Refrigerants
➢ A binary mixture consists of two pure fluids with different boiling
points.
➢ While a pure fluid exhibits constant temperature when boiling
under constant pressure, binary mixtures change temperature
during boiling.
➢ “Temperature Glide” refers to the increasing temperature during
boiling.
➢ Binary mixtures offer energy savings potential by matching the
sliding temperatures with the condenser coolant or chilled space.
➢ For mixtures, the fluid temperature also increases while heating
the sub-cooled liquid and superheating the vapor.
➢ This allows for a higher evaporating temperature and a lower
condensing pressure, which in turn increases the cycle efficiency

10. Refrigerant Fluids:
Pure Refrigerants:
➢Fluids typically used for
refrigeration are HCFCs, HFCs,
and hydrocarbons
➢While these fluids have served
the refrigeration industry for
many years, the Montreal
Protocol seeks to cap and
eventually ban the use of many
traditional refrigerants
Mixed Refrigerants:
➢Refrigerant mixtures and blends
have been the subject of extensive
research to replace phase-outs like
R-12, R-22, and R-134a
➢Most blends in use are azeotropic:
the mixture/blend behaves like a
pure fluid
➢A pure fluid under constant pressure
boiling stays at constant
temperature

11. Non-Azeotropic Refrigerant Mixtures (NARMs)
➢Non-azeotropic Refrigerant mixtures do not behave like a pure fluid
➢NARMs exhibit a phenomenon called temperature glide because the
individual components have different boiling points and under constant
pressure, the boiling process causes a temperature increase
➢Additionally, the mixture temperature increases when heating the
refrigerant from subcooled liquid and to a superheated vapor
➢Matching the sliding temperatures of the refrigerant mixture with the
cooled space (fridge/freezer cabin, air) or the condenser cooling fluid gives
the cycle a higher evaporating or lower condensing pressure, in turn
increasing the energy consumption and increasing the COP

12. Binary-Mixture Refrigeration Cycle

13. ➢ Most existing refrigerators use a single refrigerant as working
fluid; early refrigerators used R-12 (Freon) and R-22.
➢ R-134a is currently the most common refrigerant for cooling
applications, but has a high Global Warming Potential
➢ Global warming and greenhouse gases caused increased
awareness and regulation regarding chemical emissions
➢ Chlorine presence in refrigerants is known to cause ozone
depletion and is a risk to the environment
➢ The Montreal Protocol bans the production and use of
CFCs/HCFCs and sets phase-out periods for high Global
Warming Potential compounds like R-134a
Background

14. Motivation
➢Due to chemical bans and the scheduled phase-out of the popular
refrigerant R-134a, it is necessary to find new fluids for refrigerators.
➢Refrigerant fluids must be environmentally safe, compatible with
equipment and lubricants, and efficient for a cooling cycle.
➢Regulating these chemicals effectively reduces greenhouse gases
and ozone depletion as long as new fluids don’t require more energy.
➢High energy costs and emissions demand a new refrigerant fluid
that is environmentally safe/stable without consuming more
electricity.

15. New Refrigeration Fluids
➢ Research into new refrigeration fluids is mandatory for
compliance with the Montreal Protocol banning fluids that
contain chlorine
➢ An alternative approach is to create a blend of existing
refrigerants
➢ Properties of mixed refrigerants differ from their pure
components and are dependent on component weight fractions
➢ Azeotropic refrigerant mixtures behave like pure fluids
➢ Non-azeotropic refrigerant mixtures have unique boiling
properties, which offer energy savings potential for fridge/freezer
applications

16. Stakeholders
➢ Dr. Farouk (Advisor, Department of MEM)
➢ Homeowners
➢ Supermarkets
➢ Vendors
➢ Refrigeration/Appliance Companies

17. Category Design Priority Description
Aesthetics A1 2 Refrigerator exterior unphased by modification
Business B1 1 Prototyping costs within proposed budget.
Business B2 2 Increased COP over existing models.
Durability D1 1 Operating functionality remains intact for extended period
Experimentation Exp2 1
Output measurements (energy consumption) can be
recorded.
Safety Saf1 1
Binary refrigerants are compatible, nonflammable and
nonexplosive.
Safety Saf2 1
Reduces greenhouse gas emissions, environmentally
benign.
Stakeholder Needs

18. Design Methods
➢ Design Phase
○ Research into field
○ Utilization of Thermodynamic cycles and optimization algorithms
○ Refrigerant pair selection
➢ Construction Phase
○ Use of selected binary mixture
○ Charging with the optimized mass fraction
○ Utilize modern machining techniques and access to Drexel machine shop
➢Testing Phase
○ Characterization utilizing thermocouples, pressure transducers, energy
analysis
○ Confirm design goals, recording temperature and power values
○ Test for veracity of optimization method

19. Design Description: Specifications
Spec Need Priority Metric Value
1 A1 2 Refrigerator looks the same after modification Yes
2 B1 1 Prototyping cost < $500
3 B2 2 Coefficient of performance (COP) > 2.75
4 D1 1 Lifetime > 20 years
5 Exp2 1 Measurable outputs > 2
6 Saf1 1 Flammable/Explosive No
7 Saf2 1 Low greenhouse gas emissions Yes

20. Constraints and Engineering Standards
➢ Retrofitting: Binary mixture must be compatible with existing refrigerators.
○ Mixture will be a drop-in replacement, retrofit, or not compatible.
➢ Efficiency: Optimized mixture’s COP should meet or exceed current fluids.
○ Baseline refrigerant R-134a has typical COP of 3.21
➢ Safety: Mixture should not combust or react within the system.
○ Complies with occupational safety measures (OSHA)
➢ Environment: Must have ZERO Ozone Depletion Potential (ODP)
○ Minimal Global Warming Potential (baseline R-134a has GWP = 1340)

21. Design Concepts
➢ Binary refrigerant selection
○ Comparative analysis using stakeholder needs and refrigerant
properties.
➢ Thermodynamic cycle analysis
○ Choice of cycle determines objective function used in
optimization(COP equation)
➢ Optimization theory
○ Various optimization techniques exist. The choice of
optimization was influenced by the known skills of the group

22. Binary Refrigerant Selection
R125 R32
Selection
Criteria
Weight Rating Weighted Rating Weighted
Hfg 0.5 3 1.5 5 2.5
Cost 0.3 3 0.9 1 0.3
Cp 0.2 3 0.6 1 0.2
Density 0.2 3 0.6 1 0.2
Flame Limits 0.6 3 1.8 1 0.6
GWP 0.7 3 2.1 4 2.8
Total 7.5 6.6
R134A R152A
Selection
Criteria
Weight Rating Weighted Rating Weighted
Hfg 0.5 3 1.5 4 2
Cost 0.3 3 0.9 4 3.6
Cp 0.2 3 0.6 1 0.2
Density 0.2 3 0.6 2 0.4
Flame Limits 0.6 3 1.8 2 1.2
GWP 0.7 3 2.1 5 3.5
Total 7.5 10.9

23. Refrigeration Cycles:
➢The most basic refrigeration
cycles are the reverse Rankine
and Carnot cycles. These cycles
make ideal assumptions to
simplify analysis. The most
important analysis parameters
are the (COP) and the
Refrigeration Duty (Qin).

24. Constrained Optimization Theory
➢Optimization concept
○Minimize/Maximize objective function subject to constraints
➢Objective function defined
➢Constraints defined
➢Choose a constrained optimization algorithm (Method of Lagrange
Multipliers)
➢Solution yields values that minimize/maximize an output

25. Constrained Optimization Theory
➢Objective function
➢ Constraint Equations:
➢Optimization: Solve to find values
that will maximize/minimize the objective function.

26. Computer Simulation
➢MATLAB (Matrix Laboratory)
➢Availability
➢Easy to manipulate/correct
➢Supplement Optimization

27. Context and Impact: Environmental Impact
Analysis
➢ Binary Refrigerants are
compatible, nonflammable and
nonexplosive
➢ Reduced greenhouse gas
emissions, environmentally
benign
➢ Potential to reduce effect of
refrigerants on global warming
problem

28. Context and Impact: Social Impact Analysis
➢ Clean and reduced
emissions
➢ Performance optimization
➢ Energy savings

29. Context and Impact: Ethical Analysis
➢ Montreal Protocol was released to ban the use and production
of HCFC and CFC refrigerants. Therefore, the use of binary
mixtures falls into total accordance with the Montreal Protocol
without violating any ethical aspect of it
➢ Low danger in operation
➢ Lacks combustion, working fluids self contained and do not
need to be exotic
➢ Environmentally Friendly
o Reduced emissions and pollutant

30. Context and Impact: Economic Analysis
➢ For the household refrigerators, the daily
energy value is about 1400 watt-
hours/day. It is actually the greatest
power consumption of ordinary
household appliances.
Thus, the product becomes economic helpful
as following:
➢ Low maintenance, long operating life
➢ Increased COP over existing models
( higher than 2.75)
➢ Increased capacity over existing models

31. Summary and Conclusions
➢ The application of binary refrigerant mixtures for domestic fridge/freezer
appliances was extensively researched and found to be a feasible and
economical approach to alternative refrigerant fluids.
➢ Optimization processes were coded and tested against example problems in
MATLAB and showed that the results of the code correlated with known
solutions
➢ Various refrigerant mixtures were investigated and compared to determine
two pure fluids to produce a large temperature glide.
➢ The refrigerants R-125 and R-152a were selected as the best composition for
the binary mixture based on theoretical temperature glide and
flammability/safety concerns.
➢ The project will move forward with building a domestic refrigerator for the
binary mixture and experimentally determining optimal composition by varying
mass fractions.

32. Future Work
➢Strict Design, Build and Test policy
➢Yet to find the optimal mass fraction
➢Domestic refrigerator will be charged
in winter term
➢Constant communication with advisor
➢Testing in spring term to verify
analytically derived results

33. Project Budget
Item Vendor QTY Unit Cost
Total
Cost
Mini Refrigerator in Silver
Mist 3.1 cu ft HomeDepot 1 $249 $249
R152A Alibaba 10 lbs $5 $50
R125 Alibaba 10 lbs $4 $50
Universal Thermocouple
HomeDepot 4 $10 $40
Kill-A-Watt Electric Usage
Monitor Newegg 1 $19.00 $19.00
Enviro Safe Can-Tap
Gauge Sears 1 $28.00 $28.00
Line Tap Valve Amazon 1 $6.00 $6.00
Sensor 15PSI Gauge Zoro 2 $29.00 $58.00
Total $500

34. Fall Term: Schedule of Tasks
Task
Fall quarter 2014
1 2 3 4 5 6 7 8 9 10 11
22-Sep 29-Sep 6-Oct 13-Oct 20-Oct 27-Oct 3-Nov 10-Nov 17-Nov 24-Nov 1-Dec
Team Formation
Research
Budgeting
Design Development
Draft Report
Report Submission
Draft Presentation
Presentation
Prototype Design
Selection
Teamwork Assessment

35. Future Work: Schedule of Tasks
Task
Winter quarter 2015
1 2 3 4 5 6 7 8 9 10 11
5-
Jan
12-
Jan
19-
Jan
26-
Jan
2-
Feb
9-
Feb
16-
Feb
23-
Feb
2-
Mar
9-
Mar
16-
Mar
Refrigerator
purchase
Experimental set
up
Date record and
analysis
Draft Report
Report
Submission
Elevator Pitch
Preperation
Elevator Pitch
Presentation
Teamwork
Assessment
Task
Spring quarter 2015
1 2 3 4 5 6 7 8 9 10 11
30-
Mar
6-
Apr
13-
Apr
20-
Apr
27-
Apr
4-
May
11-
May
18-
May
25-
May
1-
Jun
8-
Jun
Abstract Draft
Abstract
Submission
Performance
Analysis
Draft Report
Report Submission
Draft Presentation
Final Presentation
Teamwork
Assessment

36. Acknowledgements
➢ MEM Senior Design Team #25 would like to thank our advisor,
Bakhtier Farouk for guidance throughout the project
➢ We would like to acknowledge the works of Wilbert F. Stoecker,
whose research papers inspired the investigation into the practical
application of refrigerant mixtures and the effect of sliding
temperatures for use in household fridge/freezer applications

37. Questions?