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Peer Review Project Proposal:

Refrigerant Sensor Locking Caps

Dave Philpott

Ms. Catherine Gorman

ECPI University

10 March 2014

I pledge to support the Honor System of ECPI. I will refrain from any form of academic dishonesty or deception, such as cheating or plagiarism. I am aware that as a member of the academic community, it is my responsibility to turn in all suspected violators of the honor code. I understand that any failure on my part to support the Honor System will be turned over to a Judicial Review Board for determination. I will report to the Judicial Review Board hearing if summoned.

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Project Purpose

The destruction of the ozone layer and global warming are two major environmental

concerns for our generation. Our reliance upon mechanical refrigeration for heating and cooling,

both for comfort and the preservation of goods, contributes to ozone depletion and the rise of

greenhouse gasses in the atmosphere. The problem is two-fold:

Chlorofluorocarbons (CFCs) and hydro-chlorofluorocarbons (HCFCs) were used

extensively as refrigerants until 2010. Any release of these refrigerants results in the

introduction of chlorine to the atmosphere. One

molecule of chlorine destroys 100,000 molecules

of ozone (Whitman, Johnson, Tomczyk, and

Silberstein, 2009, p. 165).

Hydrofluorocarbons (HFCs), the primary

refrigerant for automobiles since 1995 and

comfort cooling equipment since 2010, are classified as greenhouse gasses. If released,

HFCs do not deplete ozone but have global warming potential (The ESCO Institute,

2001, p. 7).

Refrigerant release also contributes to reduced unit efficiency. When system capacity is

compromised, the equipment must run longer to accomplish the same task. The energy required

to power the equipment results in greater demands on power plants, causing larger amounts of

exhaust gasses belched into the atmosphere. These gasses contain carbon dioxide, another global

warming contributor.

Minimizing refrigerant release contributes to the health of our atmosphere.

Figure 1: Refrigerant cylinder, 410A

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Hypothesis

Refrigeration units remove heat through a latent heat exchange; liquid refrigerant, boiling

at low temperatures, absorbs heat energy and becomes a vapor. A compressor compresses the

vapor to increase its temperature; the heated gas loses heat outdoors, becoming a liquid

refrigerant once more. This cycle requires a proper balance of refrigerant for efficient operation.

Technicians measure refrigerant levels by connecting a hose of a gauge manifold set to a

service port on the refrigeration unit. Refrigerant, either in liquid form or vapor form, fills the

hose; the gauge measures and displays the pressure. Because

the system pressure and pressure of the refrigerant in the hose

are equal, the refrigerant cannot re-enter the unit; it is trapped

in the hose. Removal of the hose causes the refrigerant to be

released to the atmosphere; code requires technicians to use a

specially-designed low-loss fitting to prevent such release.

The problems with this procedure are:

The refrigerant in the hose is refrigerant removed from the system.

Technicians cannot re-use the refrigerant in the hose and must recover it properly. Most

vent it to the atmosphere.

Refrigerant release could be reduced if service technicians could measure refrigerant levels and

pressures without connecting the gauge manifold set.

One other form of refrigerant release occurs when a person removes vapor from a unit for

the purpose of inhaling the refrigerant, known as “huffing.” Most refrigerants create a mild

sensation of euphoria when inhaled; abusers access the gas through the service port of a

Figure 2: Gauge manifold set

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refrigeration unit by depressing the check valve (Schrader stem), filling a small plastic bag with

vaporized refrigerant, and inhaling the contents. To combat such illegal access, units are now

required by code to be equipped with a locking cap over the access fitting.

I propose a solution to both of these issues. I believe a locking cap can be equipped with

a pressure sensor and wireless transmission technology so that refrigerant pressure can be

monitored through a software application without the need for

connecting the gauge manifold set. This fitting could also be

equipped with a thermocouple to monitor the physical

temperature of the refrigerant line; this enables the technician to

measure superheat and subcooling in the system. Superheat (vapor) and

subcooling (liquid) tell the technician if the system is properly charged and if it is efficiently

absorbing and rejecting heat. Use of this fitting prevents illegal access to the refrigerant while

enabling a technician to monitor refrigerant levels without loss.

Solving the Problem

The locking cap must meet the following criteria:

It must meet specifications for a code-approved locking cap.

It should contain a pressure sensor for continuous monitoring of refrigerant pressure.

It should contain a thermocouple for continuous measurement of sensible refrigerant line

temperature.

It should contain technology for wirelessly transmitting data.

It must be small enough for practical use.

It must be durable enough for continuous outdoor use.

It must be priced to encourage wide-spread use in the HVAC industry.

Figure 3: Locking caps

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Right now, the technology for all of the above criteria exists in separate forms. I need to

aggregate the separate constituents into a single component.

Intended Audience

People all over the world use refrigeration units. These units can be used to preserve

products, keeping them frozen or cold for storage and transportation. These units can also be

used for comfort; air-conditioners keep spaces cool and dry; heat pumps use refrigeration to act

as both air-conditioning and heating units. The component I propose could help home owners

with comfort costs; it could also help business owners such as grocers and restaurant owners

with refrigeration needs in addition to comfort costs. Reduction of ozone depletion and global

warming concerns affect everyone on the planet.

Research and Discussion of Sources

To meet the criteria for the proposed device, the following must be researched:

Code requirements for the locking cap will be determined through the International

Mechanical Code book and correspondence with NOVENT, the manufacturer of

refrigerant locking caps. These resources will provide the basic design of the component.

Refrigerant pressure sensors will be researched through correspondence with Sensata, a

manufacturer of refrigerant sensors and transducers; and Bartec USA, a leading

manufacturer of wireless tire pressure management systems (TPMS) that offer similar

technology to what I am proposing.

Wireless thermocouple technology will be researched through correspondence with Birk,

a company specializing in thermocouple engineering. The thermocouple may be an

optional feature; temperature sensing is essential to determining superheat and subcooling

as is therefore important to the technician. I believe it to be an essential feature.

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Wireless data transfer will be researched through correspondence with LORD

Microstrain, a company specializing in wireless networks for small sensor applications

and through two texts: Electronic Communications: Principles and Systems (Thomson

Delmar Learning) and Electronic Communication Systems (Delmar Cengage Learning).

My first choice for wireless transmission is Bluetooth, as the technology implements a

common frequency spectrum (2 – 2.4 GHz) but avoids interference through frequency

hopping technology.

These resources are referenced as:

Blake, R. (2002). Electronic communication systems (2nd ed.). Clifton Park, NY: Delmar.

Stanley, W. and Jeffords, J. (2006). Electronic communications: Principles and systems. Clifton

Park, NY: Thomson Delmar.

http://www.bartecusa.com/. Retrieved 9 March 2014.

http://www.birkmfg.com/thermocouples.html. Retrieved 9 March 2014.

http://www.microstrain.com/wireless/sensors?gclid=CJD___yChr0CFYY7MgodDkAAsw.

Retrieved 9 March 2014.

http://www.noventcaps.com/. Retrieved 9 March 2014.

http://www.sensata.com/sensors/pressure-sensor-hvac.htm. Retrieved 9 March 2014.

I hope to use these references as sources of information to develop a proposal. I do not

expect the individual companies to divulge proprietary information on their respective

intellectual property; rather, I hope to gain some insight as to how the separate technologies may

be assembled. The goal would be a product manufactured from original engineered

specifications; however, a prototype may be fabricated from parts purchased from these separate

sources.

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References

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The ESCO Institute. (2001). EPA certification exam preparatory manual. Mount Prospect, IL:

ESCO Press.

Whitman, W., Johnson, W., Tomczyk, J., & Silberstein, E. (2009). Refrigeration & air

conditioning technology (6th ed.). Clifton Park, NY: Delmar.

Figure 1: http://image.made-in-china.com/43f34j00ZjsQycHzEDoP/30lb-Cylinder-Refrigerant-

R410A.jpg. Retrieved 9 March 2014.

Figure 2: http://static.coleparmer.com/large_images/07164_57.jpg. Retrieved 9 March 2014.

Figure 3: http://pump.rectorseal.com/wp-content/uploads/2013/03/no-vent-caps.png. Retrieved 9

March 2014.