Patent Application
20180070659
The present disclosure relates generally to wearable cooling and warming systems, and more particularly to a personal cooling and warming garment system based on the phase change material (PCM) energy storage.
The high temperature of summer and cold weather in winter make people want only to hide in the air-conditioned room. In this case, it is efficient to cool or warm the air indoors to make the individual comfortable. But when the individual comes outdoors and is exposed to the external environment, the traditional form of air conditioning, as mentioned above, is not available. A wearable temperature control garment system can be a good solution to the problem, providing individuals with effective cooling or heating when individuals are outdoors.
Different types of warming or cooling garments have appeared in many patents, and there have been several products on the market. For example, U.S. Pat. No. 6,295,648 to Moshe Siman-Tov in discloses an air-cooled garment that protects individuals against heat stress by circulate ambient air or cooled and dry air over the body. This arrangement enhances heat removal by convection and sweat evaporation, but is efficient only when the skin is saturated with sweat. Under that circumstance, individuals is already overheated and feeling uncomfortable. Also, air-cooled garment can only achieve cooling, not heating. The same shortcomings exist in the air-cooled garment in U.S. Pat. No. 6,295,648, which creates cold gas by rapid expansion of the compressed gas.
U.S. Pat. No. 6,134,714 discloses an enhanced personal cooling garment. The garment contain liquid water in the bladder between layers which is only permeable to water vapor. When the garment is worn in direct contacting with the wearer's skin, the liquid water diffuses as vapor through the outer layer and remove latent heat required for evaporation, hence cooling the human body. But this method causes the air of the body surface with high humidity, which will resist sweat evaporation and make individuals feel uncomfortable. And this kind of cooling garment cannot achieve heating.
Some other portable conditioning garments are fluid cooled, as shown in U.S. Pat. No. 7,000,682. Cool or hot liquid is circuited inside tubes embedded in a garment with the help of a battery-powered pump. Liquid is conditioned by cold or heat tank to keep the liquid cool of hot. So the wearer need not only wear the garment, but also carry a pump, a battery and a tank or even a compressor.
As a result, it is desirable to have a wearable temperature control system that is more comfortable, portable, breathable, and can achieve cooling and heating.
This disclosure provides a more comfortable, wearable temperature control system that is worn by wearers indoors or outdoors, which directly contacts the skin to achieve cooling or heating. An embodiment of the wearable temperature control system disclosed therein is separable. When the user stays outdoors or moving, disconnecting the system and only carrying a part of it can reduce weight.
In another embodiment, the wearable temperature control system utilizing the phase change material, and when the PCM relief its energy for reusing, the garment is still available for individuals to achieve cooling or heating.
In a specific embodiment, the wearable temperature control system comprises two separable parts: a garment and an external heat pump that works as a heat pump in cooling mode and a heat source in heating mode. The garment worn adjacent to the skin by the wearers for cooling or heating depending on the heat absorption or heat release of phase change materials capsules, which are distributed evenly uniformly on a layer in the garment, whereby to provide the wearers with a comfortable and healthy environment. It is not necessary to have fan, pump, battery and like device attached to the garment, making it light and portable for wearers to walk or work outdoors. In addition, when PCM in the garment needs to be recharged, wearers do not have to take off the garment and put the PCM in a specially cold or hot environment, such as refrigerator or a heater. Wearers only need to connect the garment with the external heat pump via the connecting pipe, cold or hot water supplied by the heat pump will flow into water tubes embedded in the PCM in the garment and exchange heat with the PCM, which makes the garment wearable even when the PCM is being recharged.
Further features and objects will be more fully disclosed from the following detailed description of the preferred embodiment of the present invention with reference to the accompanying drawings, in which:
In this embodiment, the garment is in the form of jumpsuit, which covers the upper limbs and the torso so that the total covering area accounts as much as about 48% of the whole body surface. Such a design accomplishes body regional cooling or heating, instead of cooling the whole body, which improves convenience and maintain adequate preservation of thermal comfort. Studies has shown that cooling the torso is more effective in relieving heat stress than cooling other parts of the body. The garment is preferably worn directly adjacent to the skin, and may be worn without any outer clothing. In order to be more conveniently to put on and take off the garment, there are zippers 8 in the front of the chest and along the inner side of the thigh.
As shown in
PCM capsules 4 exchange heat with the human body, keeping the wearer in heat balance. The heat transfer depends on the temperature gradient between the inner liner 6 and the wearer's body surface. High conductivity of the inner liner and lower temperature of PCM increases the thermal gradient. The temperature is preferably kept at or above 22° C. It is also important to the garment's function that the inner liner 6 is flexible and fits closely with the wearer's body, which ensures a good thermal transmission between PCM capsules 4 and the wearer's body. Cotton is suitable for the inner layer because it is stretchable, soft and breathable. The cotton fabric can be very thin to reduce the heat resistance. This inner liner is fixed on the garment by snapping at the edge of the liner. The wearer may take down the liner for cleaning or change.
Between the inner liner 6 and the insulated material 3, namely the middle layer, is a carrier (not shown in the drawing figures) that supports PCM capsules 4. In order to distribute PCM capsules 4 uniformly in the carrier material, the carrier is made from a material having a porous and reticulated structure, within which the PCM capsules reside. Such a design maintains flexibility so that the PCM capsules can conform to movement of the wearer. The PCM capsules have spaces between them that allows moisture to diffuse. Soft and flexible capillary tube 5 is embedded in PCM capsules 4 and is preferably in the form of network, providing convoluted flow paths along each part of the garment—front, back and upper limbs. The capillary tube 5 has an inlet and an outlet which are located at the port 7 on the side of the garment. When the garment is connected to the heat pump by inserting the connecting tube 15 of the micro pump 2 into the port 7, cold or hot water from the heat pump 2 enters into the capillary tube 5 of the garment through the port 7, and exchange heat with the PCM capsules 4.
PCM capsules 4 that has an appropriate melting/freezing temperature responds quickly according to the temperature of the water in the capillary tube 5. The PCM capsules encapsulate a PCM material so that it does not leak out. If the water is hot, the PCM capsules absorb heat and store the thermal energy. If the temperature of the PCM capsule exceeds the melting point of the PCM material, the PCM material would soften and/or melt. If the water is cold, the PCM material releases this stored thermal energy and would solidify, which is a recharging process. After the water is warmed or cooled by the PCM capsules, it is circulated to the heat pump 2 for re-cooling or re-heating. At the same time, PCM capsules exchange heat with the wearer's body by means of heat conduction of the inner liner to cool or warm the human body. Thereby the garment 1 is free from pre-freeze or preheat. Once PCM capsules are fully recharged, the garment 1 can be disconnected from the external heat pump 2, which allows the wearer to move or work easily outdoors wearing only the portable garment.
The garment includes an outer insulating layer 3. Preferably, the insulating layer is made from material like wool or down that is soft, stretchable, breathable and with high insulating factor. The insulating layer is affixed to the garment in the same way as the inner layer which allows the wearer to select preferred garment styles.
In addition, the wearer, in the comfortable state, must dissipate sweat moisture, not merely excess heat. Therefore, the garment, as a whole, must be breathable enough, namely each layer of the garment breathable enough as stated earlier, so that moisture generated by the wearer can be expelled from the skin and discharged into the environment.
The role of the external heat pump 2 is to supply cold water or hot water for the garment 1, and has compressor 11, throttle valve 12, condenser 13, evaporator 14, four way reversing valve 15, fan 16, refrigerant 17, pump 18, check valve 24 and box 25, and the added water tank upstream of the compressor. There are a season switch 26, bolt 28, a signal lamp 27 and a connecting tube 21 on the heat pump's box. When the user connects the garment with the heat pump by inserting the connecting tube into the port 7 on the side of the garment, insert the bolt 21 into socket and twist the season switch 19 on the heat pump's box 18, the heat pump 2 will make cool or hot water for the garment 1, and the water is delivered to the garment by the pump 18. The season switch 19 has three positions: “off,” “summer” for cold water and ‘winter’ for hot water. The connecting tube is insulated, having two inner plastic hoses for supply and return water, wrapped and separated by the insulation material. The end of the connecting tube is provided with a dry-break style connector. The dry-break style connector is designed to be pressed into the port on the garment and close automatically when disconnected, preventing any possible water leakage. When the garment is fully recharged, the signal lamp lit to notify the wearer.
This wearable system has four operation modes: 1. Cool storage and cooling mode; 2. Cooling mode; 3. Heat storage and heating mode; and 4. Heating mode. Cool storage and cooling mode, as the name implies, achieves cooling for the wearer and recharges the PCM. In this mode, the garment is connected to the heat pump, the season switch is on the summer position, and then the heat pump will supply cold water for the garment. The system can be switched to the Cooling mode by disconnecting the garment from the heat pump. This mode just achieves cooling for the wearer by absorbing the wearer's body heat using the cold PCM, which may melt after being heated up. Similarly, Heat storage and heating mode achieve heating for the individual and recharge the PCM. In this mode, the garment is connected to the heat pump, the season switch is on the winter position, and then the heat pump will supply hot water for the garment. The system can be switched to the Heating mode by disconnecting the garment from the heat pump. This mode just achieves heating for the individual by solidifying PCM.
The total heat gain, which includes the internal heat gain and the external heat gain, is calculated as follows:
A=A
D
*C (1)
A
D=0.202mb0.425H0.725 (2)
A=covering area of the garment, m2
AD=human body surface area, m2
C=the percentage of the garment covering area accounting for body area, %
H=height, m2
mb=mass, kg
For a 1.75 m tall and 65 kg man, the total surface area is 1.8 m2. According to the somatology, the area percentage C covered by the garment is 48% (27%+4%+5%+12%). As a result, the covering area of the garment fitting such a man is about 0.862 m2.
Q=M*A (3)
where
Q=internal heat gain, W
M=metabolic rate, W/m2
Metabolic rate varies over a wide range, depending on the activity, person, and conditions under which the activity is performed. The metabolic rates for an average adult (AD=1.8 m2) whose activities is typing indoors or walking at the speed of 1.2 m/s outdoors is respectively 65 W/m2 and 115 W/m2. So the internal heat gain indoors is 54.99 W, and outdoors 99.35 W. Considering the evaporative heat loss accounting for ¼ of the sensible heat loss when comfortable, so the heat absorbed by PCM capsules is about 43.99 W indoors and 79.5 W outdoors.
The heat generated is absorbed by the PCM material by conductive heat exchange with the inner liner. Heat conduction equation is
q=(tsk−tPCM)*A/Iclo1 (4)
where
q=sensible heat absorbed by PCM, W
tsk=skin temperature, ° C.
tPCM=melting/freezing temperature of the PCM material, ° C.
Iclo1=heat resistance of inner liner, ° C.·m2/W
From the previous calculation, A=0.864 m2, q=43.99 W indoors or 79.5 W outdoors. Studies show that the skin temperature is kept at about 33° C. when comfortable. Assuming the heat resistance of inner liner Iclo1=0.054° C.·m2/W, as a result, melting/freezing temperature of the PCM is about 28.3° C. In this design, the PCM temperature is set from 25-30° C. for optimal performance.
The heat exchange with the outside environment consists of three parts:
Solar radiation (Direct solar radiation, Sky diffuse radiation, Ground reflected radiation), long-wave radiation (atmospheric longwave radiation, Ground long-wave radiation, Environmental surfaces long-wave radiation) and the convection with the environment. Equations below describe the total external heat gain. The coefficient h governs exchange by convection from the exposed garment surface to the surrounding environment, and it is relevant to the surrounding wind speed, which is described in the following equations (5)-(7).
q=h
c(tair−tw)+aI−Qlw (5)
h
cin=2.7+8.7*v0.67 (6)
h
cout=3.1 W/m2K (7)
q=total external heat gain, W
hcin=convection heat transfer coefficient indoors, W/m2
hcout=convection heat transfer coefficient outdoors, W/m2
tair=ambient air temperature, ° C.
tw=The surface temperature of the garment, ° C.
a=absorption factor of solar radiation
I=solar radiation intensity, W/m2
Qlw=Long-wave radiation heat exchange, W
v=surrounding wind speed, m/s
Using Washington D.C. as an example, climatic design condition is the winter design day and summer design day. On the summer design day, dry-bulb temperature=34.6° C., wet-bulb temperature=28.2° C., wind speed=3.4 m/s; on the winter design day, relative humidity=−1.2° C., relative humidity=74%, wind speed=3.3 m/s. From the historical date, solar radiation intensity in summer is about 800 W/m2, and in winter is about 60 W/m2.
Because the external heat gain varies according to the environment, the solutions differ under the following four conditions. During the summer outdoors, hcout=22.45 W/m2K. Then, neglecting the long-wave radiation heat exchange in the day time, from the equation (8), the total external heat is
q=1096.77−22.45tw (8)
During the summer indoors, from the equation (7), hcin=3.1 W/m2K, and there is only the convection with the environment. From the equation (6), the total external heat gain is
q=107.26−3.1tw (9)
Similarly, the total external heat gain during the winter outdoors is
q=−21.53+22.06tw (10)
and the total external heat gain during the winter indoors is
Q=−3.72−3.1tw (11)
The heat conduction of the insulation:
q=(tw−tin)/Iclo2 (12)
tin=the interface temperature of the garment, ° C.
Iclo2=heat resistance of the insulation, ° C.·m2/W
Assume the heat resistance of the insulation Iclo2=0.21° C.·m2/W, and tin=tPCM.
According to the heat balance:
h
c(tair−tw)+aI−Qlw=(tw−tin)/Iclo2 (13)
Finally the total external heat gain and temperature at the insulation's surface in the four conditions are respectively
t
w=45.3° C., q=80.8 W
t
w=30.8° C., q=11.9 W
t
w=28.3° C., q=19.87 W
t
w=5.83° C., q=107W
In alternative embodiments, the wearable system is configured to either cooling or heating the wearer. In such cases, the heat pump is replaced by either a chiller or a heater. The chiller can only chill the water while the heater can only heat the water.
