Title of Invention

"MULTIPLE TRANSFORMATIONS PHASE CHANGE MATERIAL (MTPCM) FOR PASSIVE TEMPERATURE REGULATIONS"

Abstract

The present invention provides a multiple transformation phase change materials (MTPCM) for passive temperature regulations comprising hypo eutectoid and hyper eutectoid solid solutions of binary systems of fatty acids. Said MTPCM shows multiple phase changes in 30- 600C range and easy phase reversal in tropical nights and thus are more useful in passive heating/ cooling applications in extreme climates than conventional single phase change materials. These materials can be filled in metallic or FRP cavities to make panels for passive cooling/ heating applications in permanent/ temporary buildings and structures.

Full Text

FIELD OF INVENTION: The present invention is related to a multiple transformation phase change materials (MTPCM) for passive temperature regulations comprising hypo eutectoid and hyper eutectoid solid solutions of binary systems of fatty acids. More particularly, multiple transformation phase change materials (MTPCM) which exhibits more than one phase changes in 30-60 °C temperature range and which can be utilized for passive temperature regulation in temporary/ permanent buildings/ structures and temperature sensitive instruments and equipments in extreme climatic conditions. BACKGROUND OF THE INVENTION: Temperature regulation around human body temperature in residential buildings/ structures is essential for survival/ comfort and good working efficiency of residents. This is more true for extreme climatic conditions like hot tropical/desert regions (ambient temperature in summer 48-50°C) or high altitude areas (ambient temperature sub zero). Along with human being, sensitive electronic / electrical instruments also require regulated temperature to work trouble free and efficiently. Conventionally permanent buildings are made up of heat insulating materials like concrete, bricks; mud etc. and temporary structures are made up of insulating boards like wood, ply, medium density fiber board, asbestos, PUF board etc. Heat insulator does not stop the heat completely. They slow down the rate of heat transfer and absorb the heat only equivalent to their sensible heat which is quite low of the order of one kilo joule per degree per kilogram of insulating material. This results into sharp rise/fall in temperature of material of construction. To take care of this problem, cooling of all type of building in hot regions and heating in cold regions is essential. Conventional cooling technologies are based on compression - expansion cycles of flour- carbon gases as in air conditioners or on heat losses in water evaporation as in air cooler. One of the disadvantages of conventional air cooling devices based on electrical compression -expansion cycle of gases is their high requirement of electrical power. Another disadvantage is that their running is quite expensive. Yet another disadvantage of them is environmental pollution as fluorocarbon gases leads to global warming. Another type of conventional air cooling devices is based on water evaporation. The main disadvantages of water based air cooling devices is their requirement of electric power and huge quantities of water as a consumable apart from their requirement of high maintenance due to corrosion. These devices also increases level of humidity in cooled air hence they become ineffective when atmospheric humidity and temperature are high as prevalent in tropical areas. A large fraction of world power consumption is being used for temperature moderation (heating or cooling) of buildings/ structures/ vehicles etc. In present age with limited energy resources and global warming as prime issues, high consumption of power in conventional cooling/ heating devices, make them unattractive and necessitate the development of passive cooling/ heating technologies which does not require or reduce power consumption. Current trend is to develop passive cooling/ heating devices based on latent heat of phase transformation of material. Phase change material (PCM) exchange good quantity of heat (100 to 200 joules per gram of material) as latent heat in a narrow temperature range of phase transformation. This phenomenon can be utilized to moderate temperatures in building and structures as high heat during day time can be consumed in phase transformation in narrow temperature range and energy is released back into environment by phase reversal when environment temperature falls below phase transition temperature during night. Thus PCM are being utilized for temperature moderation and to absorb any unwanted thermal spike passively i.e. with out the need of any external power input. The phase change can be solid to solid, solid to liquid or liquid to vapor. Generally PCM showing solid to liquid phase transformation in desired temperature range are preferred due to ease of designing, fabrication, assembly and maintenance. Conventionally a large numbers of PCM are being utilized for varied applications ranging from low temperature solar/ waste heat storage, PCM impregnated / filled panels, heat sinks for heat generating electronic equipments, cooling backup for critical components, cool vests etc. These PCM can be classified into hydrated salts, Paraffin, non paraffin organics, metallic alloy, fused salt eutectics etc. According to US patent no. 6241910 PCM like formaldehyde (methanol), acetaldehyde (ethanol), propanaldehyde (propanal), n- butyraldehyde (butanal), benzaldehyde, octolnaldehyde etc have been used for absorbing heat from a heat generating source like electronic/ electrical equipment by placing the material in between heat generator and heat sensitive device. According to another US patent No. 6235216 the increase of temperature in heat sensitive device showing heat generating conditions is prevented through the absorption of heat by providing a bicarbonate salt such as Lithium bi carbonate, sodium bicarbonate etc. Here irreversible decomposition reaction has been used for one time heat absorption purpose. Yet another US patent No. 6181558 teaches use of microencapsulated PCM for heat absorbing in electrical apparatus which produces heat while in operation. US patent application no. 20030131623 dated 17th July 2003 describes a heat pump using phase change materials. Yet another US patent application no. 20020083968 dated 4th July 2002 uses PCM for solar survival shelter. Yet another Indian patent application no. 734/DEL/2003 PCM has been used for cooling the air from 48- 50° C to below 40° C. Another US patent application no. 20050055982 directed to phase change structural insulated panels and walls has used macro encapsulated phase change materials having solid to liquid transition between 22 to 30°C like paraffin hydro carbon, salt hydrate, fatty acids and eutectic mixtures having solid to liquid transition in between 22-30°C sand witched between outer and inner heat insulating board for heat cut off in buildings. The main disadvantage of above mentioned PCM is that they show only single phase change at fixed temperature with out the possibility of fine tuning the temperature as per requirement of specific application. Other disadvantage of these material is that they do not have traces of high temperature second phase to help them in phase reversal. This, along with their low phase transition temperature (22-30 °C) makes them unsuitable for tropical climate. In tropical regions, high temperature in the night (30-32°C) does not facilitate automatic phase reversal of this low temperature single phase PCM as sufficient under cooling for phase reversal is not available. Hence these materials are not suitable for passive cooling in tropical areas. Other PCM materials (like hydrated calcium tetra nitrate etc. having phase change temperature above 40°C, although, shows phase reversal during night, but their phase transition temperature does not lie near human body temperature hence they stabilize temperature above 40°C which is not comfortable for human. The materials having phase change temperature near human body like octadecane (29-30°C), calcium chloride hex hydrate ( 29-30°C), Ecocide ( 35 - 36°C), Zinc nitrate hex hydrate ( 35-37° C ) etc. do not fulfill necessary under cooling requirement for phase reversal in natural ambient temperature cycle of tropical summer. Yet another disadvantage of many hydrated salt based phase change materials (which are otherwise preferred over paraffin, esters etc due to their easy availability and cost) are their high requirement of under cooling (>5° C below melting point) and incongruent nature of solidification whereby after few heating cooling cycles, they separated into two compounds, one having less number of attached water molecules and other a solution of compound in water. Another disadvantage of hydrated salts based PCM is their hygroscopic nature whereby they loose their phase change properties by absorbing humidity from environment. Further, disadvantage of hydrated salt PCM's are their corrosive nature towards metallic containers. Yet another disadvantage of many PCM known in the art is their irreversible nature of phase change which makes them unsuitable to repetitive heat absorption purposes as needed in lining in buildings through out the summer season. Another disadvantage of traditionally used microencapsulated PCM is their high dead load encasing material which does not change the phase and hence does not absorb significant amount of heat. Still another disadvantage of single phase change materials is that their phase position with respect to temperature is fixed and they transfer latent heat only at single temperature. Once this temperature is crossed due to completion of phase change, further change in temperature is very sharp. Still another disadvantage of some of paraffin’s like Octadecane, Ecocide etc and metal eutectics is that they are not economically viable for bulk applications as is the case in passive cooling. Due to above disadvantages, conventional single phase change PCM have limitations for their application in passive cooling /heating in extreme climates. OBJECTS OF INVENTION: The object of the present invention is to provide a new category of multiple transformation phase change materials (MTPCM) exhibiting more than one phase change in 30-60°C temperature range (zone of interest for passive cooling / heating in extreme climate). Another object of the invention is to provide multiple transformation phase change materials (MTPCM) to overcome many limitations shown by single phase change materials and hence more useful in applications like passive cooling/ heating in extreme climates. Another object of present invention is to provide MTPCM wherein one can tailor design the material so that the position of multiple phase changes (major peaks) is in the required temperature range to maximize amount of latent heat exchange and period of temperature arrest. Another object of present invention is to provide a MTPCM wherein one can design the composition such that traces of high temperature phases are present in the material. This phase solidify easily at comparatively higher temperature and provide nucleating sites for rest of the material. It ensures easy phase reversal of MTPCM even in hostile climate (as in hot desert) and overcome one of the most severe limitations shown by conventional single phase PCM. Still another objective of present invention is to provide a multiple transformation phase change materials (MTPCM) with phase reversal properties at comparatively higher temperature well above the minimum temperature observed during night of tropical regions. The temperature arrest by these materials is decided by the major constituents of phase changes (major peaks) while the under cooling requirements for phase reversal is decided by traces of high temperature phases present. Yet another object of present invention is to provide MTPCM which can show passive (with out help of external heating/ cooling) repetitive melting- solidification cycles in tune with day -night ambient temperature cycle of extreme climates like tropical summer (minimum temperature in night 30-32°C). Another object of present invention is to provide a multi phase change material for passive heating in extreme cold regions (high altitude areas) which can be easily charged (melted) by solar/ waste heat. Once molten, the material freezes slowly showing temperature arrest at multiple phase change temperatures evolving large amount of heat in the vicinity of human body temperature. Yet another object of present invention is to provide a light weight, non toxic, non corrosive MTPCM for passive cooling/heating applications in extreme climatic conditions like desert and high altitude areas at economically viable prices. Still another objective of present invention is to provide a MTPCM showing very high degree of stability in its melting- freezing cycles. Yet another object of present invention is to provide a MTPCM to decrease heat load on conventional cooling/ heating appliances and to provide a passive method of heat moderation in field conditions where conventional cooling/ heating technologies can not be applied. SUMMARY OF INVENTION: In order to obviate the drawbacks of the prior art and achieve the objects the present invention provides a multiple transformation phase change materials (MTPCM) for passive temperature regulations comprising hypo eutectoid and hyper eutectoid solid solutions of binary systems of fatty acids. Said MTPCM shows multiple phase changes in 30- 60°C range and easy phase reversal in tropical nights and thus are more useful in passive heating/ cooling applications in extreme climates than conventional single phase change materials. These materials can be filled in metallic or FRP cavities to make panels for passive cooling/ heating applications in permanent/ temporary buildings and structures. These materials can also be incorporated in heat exchangers to make low power incentive air cooling/ heating devices. These materials, after Macro/ micro encapsulation can be utilized as heat sink in electrical/ electronic heat generating devices for increasing their reliability in hot tropical (desert) regions. Packs of these materials can also be utilized to make hot/ cold personnel wears like vests and caps for extreme climates. The MTPCM are prepared by making solid solutions of binary systems of fatty acids more specifically Lauric-Palmetic acid, Palm tic acid-Satiric acid and Lauric-Stearic acids binary systems still more specifically Lauric-Palmetic binary system. These systems on mixing, forms various phases having melting point less than both the constituents of binary system. Said MTPCM are prepared by making hypo-eutectoid and hyper eutectoid alloys having eutectic, terminal solid solutions and intermediate solid solutions as multiple phases. DESCRIPTION OF FIGURES: FIG. 1: DSC CURVE FOR 60% LAURIC ACID + 40 % PALMITIC ACID FIG. 2: DSC CURVE FOR 25% LAURIC ACID + 75 % PALMITIC ACID FIG. 3: DSC CURVE FOR 63% LAURIC ACID + 37 % PALMITIC ACID FIG. 4: DSC CURVE FOR 60% LORIC ACID +40 % PAMITIC ACID AFTER 100 CYCLES OF MELTING -FREEZING DETAILED DESCRIPTION OF PROCESS: The present invention provides a multiple transformation phase change materials (MTPCM) for passive temperature regulations comprising hypo eutectoid and hyper eutectoid solid solutions of binary systems of fatty acids. Said MTPCM shows multiple phase changes in 30- 60°C range and easy phase reversal in tropical nights and thus are more useful in passive heating/ cooling applications in extreme climates than conventional single phase change materials. These materials can be filled in metallic or FRP cavities to make panels for passive cooling/ heating applications in permanent/ temporary buildings and structures. The MTPCM claimed above are prepared by mixing constituents of binary system more specifically Laurie acid and Palma tic acids in different composition ranges from 30-75%, still more specifically 35- 60% or precisely 40-50% are prepared which exhibits multiple phase changes in temperature range 30-600C. Yet another embodiment of this invention is that these MTPCM can be filled in metallic or FRP cavities to make panels for passive cooling/heating applications in permanent/ temporary buildings and structures. These materials can also be incorporated in heat exchangers to make low power incentive air cooling/heating devices. These materials, after Macro/micro encapsulation can be utilized as heat sink in electrical/electronic heat generating devices for increasing their reliability in hot tropical (desert) regions. MTPCM as claimed above are prepared by mixing the binary constituent of MTPCM in molten condition. First the constituent in majority is bring to molten condition by keeping in constant temperature hot water bath at temperature above its melting point providing sufficient margin for super heating and low viscosity to ensure proper mixing. Slowly the second constituent (as per alloy design and charge calculations) is added in the first molten material and stirring is done continuously. A digital thermometer continuously monitors the temperature. In case, temperature comes down significantly, adversely effecting mixing properties, bath temperature is increased and proper soaking time is provided while continuously stirring the mixture. The mixture, thus prepared, is subjected to two- three cycles of melting and freezing while continuously stirring the sample to ensure the homogeneity. A sample from the alloy is taken and checked on differential scanning calorimeter for number of phases present, their location on temperature line, latent heat value and degree of under cooling requirement for phase reversal. Incase any deviation from the desired designed values, the charge calculations are done again and material is prepared again. Five samples from different locations are collected and checked on Differential Scanning calorimeter for presence of various phases and latent heat of the alloy. In case the results are not same for all the five samples showing heterogeneity, the material is again melted and stirred further until the desired homogeneity is achieved. Present invention will now be explained with the help of examples. However, the scope of the present invention should not be limited to these examples as a person skilled in the art can make a lot of variations with the help of the description of the invention. EXAMPLE 1: In a clean beaker 60 gram of Analytical grade Laurie acid ( CH3 (CH2)i0 COOH, having M.P 44 °C is taken and melted by keeping it at 50°C in hot bath. Using the process described above 40 grams of Palm tic acid (CH3 (CH2) 14 COOH, M.P. 64°C is slowly added to molten Laurie acid to prepare an alloy of 40 % Palm tic acid- 60 % Laurie acid (by weight). The sample was characterized on Differential scanning calorimeter model DSC Q10 make M/S Water India limited. Results are shown in Fig.1. Sample shows two major peaks of phase transformations at 35.88, 39.37°C and trace of high temperature phase at 42.48°C with total latent heat of 169.4 Joule per gram and start of phase reversal at 35.87°C. This material can be used for passive cooling applications in hot tropical climate. EXAMPLE 2; Similarly using the process described above an alloy of 75 % Plasmatic acid - 25 % Laurie acid (by weight) and characterized using DSC (FIG2). The material shows four phase changes at 34.6, 39.05, 43.51 and 54.62°C with total latent heat absorption equal to 185 J/g and phase reversal starting at 48.49°C. The material will be useful for making heat sinks for heat sensitive electronic/ electrical equipments to improve their operational temperature range and for improved reliability in hot desert climate. EXAMPLE 3: Similarly using process described above an alloy of 37 % Plasmatic acid- 63 % Laurie acid ( by weight ) was prepared and characterized by DSC ( FIG 3 ). The alloy shows two peaks, one major peak at 35.88°C and a minor peak at 38.74°C with total latent heat absorption equal to 169.3 J/g and phase reversal starting at 35.02°C. The alloy will be suitable for passive cooling applications in desert areas. EXAMPLE 4; Material prepared under example 1 was given repetitive melting freezing cycles. The samples were taken after 100, cycles and characterized by (DSC FIG.4) The sample shows two major peaks at 34.9 and 39.7 OC with latent heat value of 164.6 Joule/gram and start of phase reversal at 36.110C. Thus the sample shows no appreciable change in position of major peaks, latent heat value and phase reversal temperature from the original sample (fig.1). We claim: 1. Multiple transformation phase change materials (MTPCM) for passive temperature regulations comprising a hypo eutectoid and hyper eutectoid solid solutions of binary systems of fatty acids. 2. Multiple transformation phase change materials (MTPCM) as claimed in claiml,wherein the binary system of fatty acids is selected from the group consisting of lauric acid (dodecanoic acid)-palmitic acid (hexadecanoic acid), palmitic acid (hexadecanoic acid)- stearic acid (hexadecanoic acid) or Lauric acid (dodecanoic acid)-stearic acid (hexadecanoic acid). 3. Multiple transfonnation phase change materials (MTPCM) as claimed in claim 1, wherein binary system is in composition ranges from 30-75%. 4. Multiple transformation phase change materials (MTPCM) as claimed in claiml,wherein the said fatty acid binary system comprises of lauric acid (dodecanoic acid)-palmitic acid (hexadecanoic acid) in composition range of 35- 60% more particularly 40-50%. 5. Process for the preparation of multiple transformation phase change materials as claimed in claim 1 comprising (i) melting the major constituent by keeping in a constant temperature hot water bath maintained above the melting point of the constituent, (ii) adding the other constituent to the molten material while constantly stirring the mixture, (iii) subjecting the composition to 2-3 melting-freezing cycles ensuring homogeneity. 6. A process of preparing the MTPCM as clamed in claim 5, wherein palmitic acid is added to molten lauric acid at 50°C. 7. A process of preparing MTPCM as claimed in claim 5, wherein 37-75% of palmitic acid is added to 25-63% of molten lauric acid generating MTPCM with two major phase transformation peaks between 34-36°C and 38-40°C respectively and trace of high temperature transformation in the range of 42-44°C. 8. Multiple transformation phase change materials (MTPCM) exhibiting more than one phase changes in 30-60°C temperature range and suitable for passive temperature regulation in buildings/ structures and temperature sensitive instruments and equipments in extreme climatic condition substantially as herein described with reference to the foregoing examples. Dated this 29*" day of October 2007 \Sy^y^ \ Vcry^ \ j Vidis^aGarg Of Anand and Anand A'avocates Attorney for the Applicant

Documents:

2258-del-2007-abstract.pdf

2258-del-2007-Claims-(27-08-2013).pdf

2258-del-2007-claims.pdf

2258-del-2007-correspondence-others 1.pdf

2258-del-2007-Correspondence-Others-(27-08-2013).pdf

2258-del-2007-correspondence-others.pdf

2258-del-2007-description (complete).pdf

2258-del-2007-Drawings-(27-08-2013).pdf

2258-del-2007-drawings.pdf

2258-del-2007-form-1.pdf

2258-del-2007-form-18.pdf

2258-del-2007-form-2.pdf

2258-del-2007-Form-3-(27-08-2013).pdf

2258-del-2007-form-3.pdf