Dangers of Heat Exhaustion

Transcription

1 Nils Backe Literature Review Dangers of Heat Exhaustion When an animal suffers from excess heat, it may experience heat exhaustion. Some symptoms of heat exhaustion are dehydration, light headedness, weakness, and fatigue. When a case of heat exhaustion becomes severe enough, it can result in heat stroke, which can cause permanent damage to the body ( Heat Exhaustion, 2016). In as little as 30 minutes, an infant locked in a parked car in the warm sun can suffer from heat stress and may even result in death (Dadour, 2010). As seen in Figure 1, in 2016, a total of 39 children have been victims of heatstroke deaths; this number constitutes large increase from the 24 child victims in Since 1998, the average number of child deaths due to heat exhaustion in a vehicle is 37 per year. Most of these fatalities are of children that are 2 years old or younger. (Null, 2016) Figure 1 A chart comparing the number of child deaths due to heatstroke in vehicles in the United States to the corresponding year (Null, 2016).

2 The majority of child heatstroke deaths in vehicles are caused by negligence of the attendant who is responsible for the child. Two-fifths of the states in the United States have laws pertaining to leaving a child unattended in a vehicle, whereas the remaining majority of the states do not have unattended child laws. Ten states have Good Samaritan Laws which defend a person who attempts to intervene when he or she witnesses a child locked in a hot parked vehicle. As seen in Figure 2, most child heatstroke deaths occur in the Southern portion of the United States because of the higher temperatures and warmer climate. (Null, 2016) Figure 2 A map depicting the locations of heatstroke deaths in vehicles among children in the first ten months of The locations are centered around the Southeast United States, with the most deaths occurring in Texas (Null, 2016).

3 Causes of Vehicle Heating Light Energy Humans can only see light within the visible light spectrum. An object appears a color to the human eye because it reflects the wavelengths of light that are of the same color as the object. A white object reflects every wavelength of light in the spectrum, which also means that it absorbs little light energy. A black object does not reflect any light and instead absorbs it all. The light energy absorbed into an object can turn into heat energy, which is why black colored vehicles are often warmer than white colored vehicles. Almost all of the heat energy that builds up in the interior of a parked car is created from the light energy from the sun. (David, 2014) The quality of a vehicle that affects the cabin temperature the most is the color of the vehicle. According to a study performed in 2010 in Western Australia, the interior of a parked black colored vehicle can reach temperatures that are 5 C warmer than the maximum temperature reached in a white colored vehicle (Dadour, 2010). A glossy and metallic colored vehicle would theoretically absorb the least light energy, thus reflecting the most light. Another quality of a vehicle that affects the interior temperature is the material and color of the upholstery (David, 2014). The same principal applies here, the darker the material the hotter the surface of the material gets because more light energy is absorbed. The Greenhouse Effect The interior of a vehicle is similar to a greenhouse because a portion of the sun s radiation shining on the car becomes trapped in the cabin of the vehicle. The radiation that impacts the metal surface of the vehicle can be either reflected or absorbed. This means that a

4 very limited amount of radiation that hits the metal surface actually helps heat up the cabin of the vehicle (Fowkes, 2016). As shown in Figure 3, the majority of the temperature increase is caused by the radiation that goes through the vehicle s glass surfaces. Because glass is transparent to light radiation, light travels right through the glass and gets absorbed in the dashboard or the seats of the vehicle, thus heating the interior of the automobile. Within the cabin of a vehicle, differential surface heating causes convection currents which stir up the air and redistribute the air to all parts of the cabin. (Dadour, 2010) However, the inside of a vehicle is not completely enclosed, such as the air conditioning intake and exhaust, which causes a portion of the heat to be lost. Heat loss in the cabin of a vehicle car occur by conduction through the surfaces of the vehicle as well as any other environmental exchanges. Also, hot air can leak out of the cabin of the vehicle if the windows of the vehicle are left open. (Dadour, 2010) Figure 3 A computer generated visual representation of how the sun s shortwave radiation enters a parked enclosed vehicle. Also, the present numerical values show how the internal air temperature (given in Fahrenheit) is much higher than the ambient temperature in the elapsed time (Null, 2016).

5 Figure 4 A graph comparing the increase of temperature inside an enclosed vehicle above the ambient temperature to the elapsed time in minutes. After 4 hours, the internal temperature can be as high as 55 F above the ambient temperature (Null, 2016). Air Circulation in Vehicles Most modern vehicles are equipped with a recirculation button on the dashboard. This button causes the vehicle s cooling system to draw air from the cabin of the vehicle rather than from outside. This feature can be useful in situations such as when the interior air temperature is cooler than the air temperature outside of the car. Because the cooling system is fed cooler air in this scenario, less energy is required to cool the interior air to the desired temperature. However, this button cannot be used when the vehicle is parked and turned off because it requires power to run the cooling system. (Rod, 2014) Without any modification, most vehicles have little to no ventilation when powered off, therefore high temperatures are present inside the cabins of these vehicles when parked in the

6 sun. However, some car manufacturers including BMW and Toyota have implemented a new design that uses the vehicle s battery to power the internal fans. The problem with this approach is that the fans cannot stay on for long; they can only be run for up to 30 minutes to maintain enough charge in the battery to start the vehicle. (Lacey, 2013) Solar Panels Solar panels provide a renewable energy source to power electronic device or charge batteries. Solar panels are commonly referred to as photovoltaic cells, or PV, for their ability to convert light (photo) into electric (voltaic) energy. Although solar panels use a renewable energy source (Bocci, 2012), they do not produce as much energy as common power sources do such as fossil fuels. Solar panels may be found on rooftops, near road signs, or even mounted on spacecraft (Dhar, 2013). Solar panels are made up of a multitude of individual solar cells each internally composed of a semi-conductor, that is most commonly made of silicon. There are two layers of this silicon, the top and bottom, which are coated in a charged substance. The top is usually coated with negatively charged phosphorus, whereas the bottom is usually coated with positively charged boron. Particles of light, from the sun or an artificial light source, free electrons from the atoms, generating a flow of electricity. This electric field pushes electrons to the edge of the solar panel, where they meet conductor plates. The conductor plates then convert the free electrons into a usable form of electricity. This electricity is then run through a series of wires to a power consuming device or a battery. (Dhar, 2013)

7 How Drivers Try to Cool Their Vehicle When a driver reenters his or her car after it has been parked in the sun for the majority of the day, the internal temperature of the car will frequently be uncomfortable to the driver. The most common method used to resolve this issue is to turn on the vehicle s air conditioner. A vehicle s air conditioner is similar to most other air conditioners: its main functions are to reduce the temperature and the humidity of the intake air ( How Air Conditioning, 2016). Another method that drivers undertake is to leave a gap above each of the windows to allow air to circulate through the car while it is parked. This allows outside air to disseminate into the interior of the vehicle and hot interior air to escape until thermal equilibrium is met. This method does not actually cool air, it instead provides circulation into the cabin of the vehicle. Drivers also try to prevent drastic increases in the interior temperature of their vehicle by placing cardboard against the inside of the front windshield. This approach mitigates heat transfer by blocking a portion of the sun s radiation from entering the inside of the vehicle and being absorbed in the interior materials. (Sundhar, 1989). Problems with these Methods Although a vehicle s air conditioner can be very effective at maintaining a cool temperature inside of the vehicle, it takes minutes to begin to cool the vehicle effectively. The air conditioner has not begun actually cooling the air until it has reached its full effectiveness. Once this state is reached, the air conditioner can begin to cool the intake air, which from that point takes even more time ( Patent Application ). However, even when the air conditioner first reaches its full effectiveness, the internal temperature may still be considerably higher

8 than the outside temperature. Another disadvantage of a vehicle s air conditioner is the immense power required for operation, which can be up to 500 W. This requirement also means that the vehicle must be running and supplying power to the air conditioner in order for it to run. Furthermore, a vehicle s air conditioner is prone to failure and some models can be particularly faulty, depending on the car manufacturer and assembly date (Sundhar, 1989). Some drivers leave their vehicle s windows cracked open to allow air to circulate through their vehicle while it is parked in the sun. One issue of this technique is the associated security risk: if the gap left open by the open windows is large enough to fit a hand through, personal items are at risk of being stolen. In addition to this, the gap opens the vehicle to the environment, which allows for birds and insects to enter the exposed vehicle. This method also does not actually cool the internal temperature. Theoretically, it will simply neutralize the internal temperature with the outside temperature. However, because the vehicle is continually heating up as time progresses, the internal temperature will always be warmer than the outside temperature. (Dadour, 2010) Another method is to place cardboard along the inside of the windshield. This method is cheap to perform but not very effective. All of the other windows of the vehicle are still exposed to the sun and easily allow for the sun s radiation to pass through them (Dadour, 2010). Out of these three proposed methods, the most effective would be a combination of all three. However, the difference in temperature between an unmodified vehicle and a vehicle with the mentioned temperature reducing modifications will not be very significant or noticeable. (Sundhar, 1989).

9 Current Solutions to this Problem Several independent inventors and large commercial companies have engineered a product in order to solve this problem. One of these inventions is a solar powered air conditioning system for a parked car. This patent, granted to Shaam P. Sundhar, is comprised of a single solar panel mounted in the interior of the car near the front windshield that acts as a power source and a cooling unit located in the trunk of the vehicle. The cooling unit is composed of an insulated wall, a heat sink, and an exhaust fan for the unwanted hot air. The cooling unit provides cool air to the inside of the vehicle at an efficient rate, however, the solar panels must be unfolded and placed on the dashboard of the car each time the user wishes to use the device. (Sundhar, 1989) Another independent invention, invented by Arun K. Pal called Kar-Kool, serves a very similar purpose was. This filed patent describes a cooling device for a parked automotive vehicle that features a water reservoir and fans. An onboard water atomizer releases water directly into the interior of the vehicle, inducing heat evaporation. The fans and water mister are both powered by a solar panel. The water reservoir can either be placed in the trunk or on one of the passenger s seats of the vehicle, however, this causes cargo space within the vehicle to be sacrificed. (Pal, 1994) One example of a commercial product that fulfills the same purpose in yet a different way is called IcyBreeze. IcyBreeze is a portable air conditioning unit placed in a plastic drink cooler with wheels for added mobility. The unit must be filled with water that gets dispersed through a radiator. The unit s power source is a rechargeable battery that powers the integrated fan that blows air through the radiator. The company claims that the output air is

10 35 C cooler than the external temperature. This device is more commonly used outside next to a pool or in the backyard rather than to cool the interior of a car, but it can serve either purpose equally well. ( IcyBreeze, 2016) A different patent invention that has the same function of cooling a parked automotive car was filed by David M Roberts and Albert R Snider. This invention is a detachable cooling system that is planted into the parking lot, which has a similar design to a drive-in movie theater with the sound transmitters available to each vehicle in the parking lot. Each station has a few tubes that user can hook up to their car to feed in cool air. (Roberts and Snider, 1968) Figure 5 A visual representation of Roberts and Snider s patent that depicts two cars, both of which are being cooled by their stationary invention (Roberts and Snider, 1968).

11 The Flaws of These Designs The first design, the solar powered air conditioning system invented by Sundhar, has some flaws. The first flaw is that the air conditioning unit takes up a lot of space, but the exact dimensions are not given. It can be placed in either the trunk or one of the passenger seats, which reduces the amount of usable space inside the vehicle. Moreover, even though no specific price is given, this product would most likely be quite expensive because of the solar panel and air conditioner. (Sundhar, 1989) The second design mentioned, the cooling system with the water reservoir, also has its drawbacks. Like the first design, this design also lacks compactness. The water reservoir must be placed in the trunk or the passenger s seat, which takes away precious cargo space in a vehicle. Also, with misted water constantly being sprayed into the car, the car could become moldy in the right weather conditions. In addition, if the temperature is not hot enough, the water would not evaporate, and the water would condense and stick to the interior surface of the car. This could pose a problem especially if the car has a cloth or leather interior. (Pal, 1994) The third design that was discussed, the commercially available product called IcyBreeze, also has its downsides. The base retail price for IcyBreeze is $350, which does not include any of the many available accessories and options ( Icybreeze, 2016). Additionally, this product is not solar powered, thus costing money to charge the internal battery (Yonce, 2015). The fourth design specified, the stationary detachable air conditioning system, has flaws as well. Firstly, the device is stationary, which means that an individual consumer is unable to purchase one, and the product is only practical for store or land owners. Secondly, device owners will most likely charge money to use their product if it is stationed in a private parking

12 lot. There may also may be a security risk because of the need to open a window in order to feed the tube into the vehicle. (Roberts and Snider, 1968) Engineering Plan Engineering Problem Heat from the sun's light absorbed through thermal conductivity and stored inside an enclosed motor vehicle can reach temperatures uncomfortable to humans when they come back to their parked vehicle after a hot sunny day. Engineering Goal The goal of this project is to engineer a solar powered air circulation device to neutralize the air temperature inside the cabin of a vehicle. General Methods First, four identical 80 mm computer case fans will be placed near all four of the car s side windows. Each fan has a rating of about 30 CFM, which means that each fan can move 30 cubic feet of air per minute. Each side window of the car will be opened to leave a 7 cm gap. On the left side of the car, the fans will be oriented so they blow outside air into the car, and the fans mounted on the right side of the car will be oriented so they will blow hot inside air out of the car. Each fan will be held in place by a clamp that is stuck to the inside ceiling of the cabin of the vehicle near each window to hold it in place. These four fans, each requiring about 2 W of power, will be powered by one 2.5 W solar panel mounted on top of the front dashboard under

13 the windshield connected to a sealed lead acid battery. The wires of the fans will be soldered in parallel to the wires of the battery, with the correct polarity, which will supply the power needed to operate the fans. An on/off switch will be soldered to the circuit to allow the user to choose whether they want the device running. The wiring will run around the interior ceiling of the car to all the fans and back to the solar panel on the dashboard. The effectiveness of this project will be evaluated and calculated by finding the difference of internal cabin temperatures while using the device and while the device is not installed. Also, easy installation will be taken into account. The device must be portable enough to be able to detach it and completely remove it from the car. Furthermore, low cost will be considered in order to make it affordable for the average consumer. In addition to these considerations, the durability of the device will be taken into account in order to make the device last. In order to test the device, a container that mimics the properties of the interior cabin of a motor vehicle will be used as a substitute for a car. Possible materials and size of this container are under consideration. This container will be placed in a chamber that will be heated by heat lamps. First, the inside temperature of the container will be measured at set intervals of time. The container will then be cooled down to room temperature, and my device will then be installed. With my device running, the internal temperature will be measured at the same time intervals. The difference between these two temperatures will be used to determine how effective the device is.

14 References Bocci, E., Villarini, M., Bove, L., Esposto, S., & Gasperini, V. (2012). Modeling small scale solar powered ORC unit for standalone application. Mathematical Problems in Engineering, 2012, doi: /2012/ Dadour, I. R., Almanjahie, I., Fowkes, N. D., Keady, G., & Vijayan, K. (2010). Temperature variations in a parked vehicle. Forensic Science International, 1-7. David, H. (2014). Does car colour affect car temperature? Retrieved from Dhar, M. (2013). How do solar panels work? Retrieved from Fowkes, N. (2016). In Fowkes N. (Ed.), Questions regarding "temperature variations in a parked vehicle." Heat exhaustion. (2016). Retrieved from How air conditioning works. (2016). Retrieved from IcyBreeze portable air conditioner and cooler. (2016). Retrieved from Lacey, S. (2013). BMW takes the edge off summer heat; Retrieved from Null, J. (2016). heatstroke deaths of children in vehicles. Retrieved from Pal; Arun K. (1994). Kar-kool. United States: Retrieved from =US Patents; patent application titled "fast cooling system in cars" published online (USPTO ) (2015). Atlanta, USA: NewsRx. Rod. (2014). When to use the car s recirculation button. Retrieved from

15 SNIDER ALBERT R, & ROBERTS DAVID M. (1968). Detachable air conditioner for parked automobile Retrieved from =US Sundhar, S. (1989). In Sundhar S. (Ed.), Air conditioner for parked automotive vehicle (US A ed.). United States: Yonce, D. (2015). How to keep your dog cool in a locked car... the safe way. Retrieved from