A.C. Systems has researched the current market personal cooling technology and how it is unable to maintain a worker’s body temperature while they wear Personal Protective Equipment (P.P.E.). Most cooling devices are unable to cool the body for an extended period. These devices usually use a phase change material that cool the individual by absorbing heat energy and only last for a short period of time. The phase change material usually must be changed out or replaced after around two hours which can lead to cost increases from lost work time and purchasing multiple units. Workers who wear P.P.E need a cooling device that can work longer than the current market products. There are many different markets that could use an efficient cooling device, but A.C. Systems is primarily focusing on military and police applications at this time.
A.C Systems would like to design a device which would work for an average work day of 6 to 8 hours. The device should have an approximate weight of less than six pounds. The interface for the unit should take about five minutes of instruction to learn to use the features associated with it. A.C. Systems plans to make the unit water resistant to IP7 standards, so it can be worn in most weather conditions. The primary mode of heat transfer has been identified as thermoelectric cooling with the use of a Peltier chip. Due to the use of a Peltier chip the device has the requirement of needing power. Additionally, due to portability concerns the power utilized will be from batteries.
A.C. Systems is entering the personal cooling device industry. This industry has many companies already marketing some type of cooling device. The two main competitors in the market are Occunomix and Glacier Tek. The primary function of these two competitor’s devices is through passive phase change technology. The downside of passive cooling devices is the restrictive time constraint when the phase change material completely changes to liquid. A.C. Systems intends to augment this passive technology with thermoelectric cooling to reset the material back to a solid. A.C. Systems has contacted the Reno Police Department to establish specific design considerations that would be useful in the field. Combat Veterans were also consulted to determine possible design considerations for use in combat. A literature search and a patent search has shown what materials and technologies already exist and can be integrated into A.C. Systems design.
A.C. Systems is specializing in a personal cooling device for people wearing Personal Protective Equipment. This is different from other devices on the current market that are designed more for recreational and industrial use. Most of these devices are produced and sold during the spring to allow recreational users to prepare for the heat of the summer. A.C. Systems is producing a device for police and military specifically, and therefore is able to sell the device year-round.
Proof of Concept
A.C. Systems is attempting to cool an individual’s body through the means of conduction using a phase change material and a Peltier chip. The phase change material will absorb heat energy from the body by using the proposed phase change material, coconut oil. Coconut oil was chosen because of its melting point at 79 degrees Fahrenheit. The Peltier chip will be supplied with power in an attempt to solidify the phase change material. A heat sink will be placed on the hot side of the Peltier module which will dissipate the heat to the environment. A.C. Systems is attempting to prove that the Peltier module will solidify the material so that the passive cooling will be able to recharge and absorb heat energy for an additional period of time. A.C. Systems will prove their concept works by conducting an experiment. The experiment will consist of a battery, a Peltier module and encapsulated phase change material. A.C. Systems will also be observing how much power draw is occurring to see if their current battery of choice will last for the expected timeframe.
A.C. Systems is building a personal cooling device which can be worn under personal protective equipment. This device uses a Peltier chip to solidify a phase change material which will cool the individual over a period of time. The device is made up of a Peltier chip, copper sheet, heat sink, fan, housing for heat sink and ducting for the hot air. A.C. Systems device will weigh less than two pounds, will be thin enough to fit under body armor and will be able to cool the individual for 6-8 hours. The device is intended to be placed on their back between the shoulder blades. As body temperature increases, the phase change material will absorb heat changing from a solid to a liquid. To activate the device the user pushes a button on the battery module which is worn on your belt. The Peltier chip gets hot on one side and cold on the other. The cold side of the Peltier chip is drawing heat from the phase change material solidifying the material, so it can absorb more heat from the user. A heat sink is located on the hot side of the Peltier chip and a fan is used to draw out the heat which is expelled near the back of the neck. As the individual begins to feel cool again the device can be turned off. The user repeats this process with the device until the battery is depleted or they no longer need to use the device.
The purpose of A.C. Systems device is to cool individuals who work in hot environments while wearing body armor. This device will allow individuals to do more activities before experiencing heat exhaustion or have to take a break for an extended period of time.
Electronics enclosure with battery compartment fully assembled
Cooling device with vent tube fully assembled
Adaptive Climate Systems fabricated all custom parts at the University of Nevada Reno’s machine shop. All hardware parts were purchased at ACE hardware located in the local area. The thermoelectric module, phase change material, thermal tape, switch, batteries, battery housing, tubing and fan were purchased online via Amazon Prime. Custom parts such as the gasket were CNC’d for accuracy, the thermal conductive plate and custom heat sink was sheared and drill pressed. The air-flow channel and battery enclosure was made using CAD software and then 3D printed in the machine shop. The bag containing the phase change material was cut and heat sealed using a food storage device.
Testing and Results
The testing process that A.C. Systems is going to use observes two objectives. The solidification of cocoa butter, the primary Phase Change Material (PCM), for a specific power input and how much of the PCM solidifies in a given time. Other factors during the testing process will be annotated such as the starting temperature of the PCM and the final temperature of the PCM. This will identify how much heat has been extracted by showing what level the PCM has dropped to throughout the heat extraction process. Ideally the final temperature should be below the melting point of The PCM at 81 degrees Fahrenheit.
A.C Systems tested the product by having someone wear it under a body armor vest until the PCM was completely melted. Then the Peltier module and fan was turned on to initiate the heat transfer process. Time was annotated, and levels of solidification were identified in intervals. Once the material completed the solidification process the device was then turned off and the phase melting process begins again.
Testing resulted in an average melting period of 2 hours and 28 minutes with an average RePhasing period of 30 minutes. The testing resulted in success for the project. Issues of efficiency were identified such as battery life, and ambient air temperature. Due to the time of year the ambient temperatures were suboptimal for testing. The product was designed for temperatures exceeding 90 degrees Fahrenheit and above. Another issue found while testing was not having a depleted battery indicator. The fan and Peltier module are on separate circuits with separate batteries and the Peltier battery had no visual indication of being depleted. The fan simply did not blow anymore when depleted as an indication of no power.
A.C Systems products solves the problem of heat getting trapped under body armor for military personnel and law enforcement face. These types of personnel can heat exhaustion for wearing body armor for extended periods of time. The goal of this device is to absorb the body heat under the body armor and expel it the environment. This will allow the users to wear body armor without experiencing forms of heat exhaustion. All basic design criteria was met with the final prototype designed by A.C. Systems.
Meet the Team
Matthew is from Winnemucca, Nevada. In 2014, he enrolled in the mechanical engineering program at the University of Nevada, Reno. Matthew has been involved in engineering projects for the last ten years or so. One of his biggest accomplishments was helping design a new building for a branch of his brother’s company. Matthew has also designed and built a fume hood for his jewelry hobby. Matthew graduated from GBC with an Associate’s Degree in Science, Fine Arts, and Applied Science in 2012. His current goal is to graduate from UNR with a Bachelor’s in Mechanical Engineering. After graduation, he would like to go into research and design for the automotive industry.
Pete Costopoulos is originally Pennsylvania then moved to Nevada in 2006. In 2013, he enrolled in Mechanical Engineering at the University of Nevada, Reno. His academic career has been a challenging one. During his academic career he learned how to use computer programs such as Matlab and SolidWorks. He knew nothing about these programs coming into this University. Many courses at this at this University have you work in teams. During my Introduction to Engineering course he was placed in a team of four students. The goal for this class was to create a hovercraft that could complete an obstacle course. This course taught me to take establish roles for each team member and make they are held accountable. After he Graduates in the spring of 2018, He would like to get a job in the automotive industry designing
Nathan Davey is a Marine Corps veteran with a CSWA certification and an Associates of Science degree from Truckee Meadows Community College. Furthermore, he is from Reno Nevada and currently a senior in the Mechanical Engineering program at the University of Nevada, Reno (UNR). While pursuing his undergraduate degree at UNR, he has developed the basic understanding of scientific concepts and how those concepts can be applied to everyday life. For example, while he was an intern at a local company called LSP, he was tasked to develop a cleanout plate lid that would be able to withstand a vertical center force of 15,000 foot-pounds, an ASME standard. At first, he failed repeatedly, and where he succeeded he failed again due to design parameters. However, after focused study and analysis he found the error. He was only accounting for the critical thickness required to withstand the force. Nevertheless, my focused study of force distribution and understanding of the design intent, lead him to develop a cost-effective solution. Decrease in thickness of the plate using a ribbed extruded circle on the opposing side of the force. This development saved the company money and made an old product profitable again. The experience he has gained both academically and as an intern, in the understanding of scientific applied concepts, is leading him in the direction of entrepreneurship for product development upon graduation. To achieve this, he a has taken it upon himself to understand the market and how that market maybe asking for a scientific solution.
Joseph Dwyer was raised in Rocklin, California where he graduated from Rocklin High School with 3.7 GPA with an emphasis in engineering. Graduating in 2014, he enrolled at the University of Nevada, Reno to pursue a career in mechanical engineering. At the University he joined the Greek fraternity Kappa Alpha Order. There he became the scholarship head from 2016-2017. His greatest achievement was being invited by NASA to watch Space Shuttle Discovery (STS-128) launch into space in 2009. Another proud moment of his life was completing my hovercraft project during my freshman year of college and receiving a high grade on the project. Joseph’s biggest goal right now is simply graduating next semester. After graduation he plans to work in the aerospace industry and possibly earn an M.S. in aeronautical engineering. This will help lead him to his dream of working on spacecraft.
Collin O’Boyle is a senior mechanical engineering student graduating in the spring of 2018 at the University of Nevada, Reno. Collin currently holds two associate degrees from Truckee Meadows Community College and has his associate level certification in SolidWorks 3D Cad Design Software. Additionally, Collin is a member of Phi Theta Kappa Honor society. Collin’s interests include; robotics, heat transfer, education, renewable energy and chemical energetics. Collin is from Reno, Nevada and chose to move back to Reno to attend the University of Nevada after his career as an Explosive Ordnance Disposal Specialist. His goals for the future include starting his own company and designing equipment for use by military and civilian bomb disposal personnel.
ME452 Instructors-Nich Maus, Dr. Saul Opie, Dr. Daichi Fujioka
Mentor-Dr. Yan Wang
Sponsor- Collin O’Boyle
Machinist- Brian Nagy
Special thanks to
Reno Police Department
Rocklin Police Department
University of Nevada Police Department