Claims:The scope of invention is defined by following claims:

Claim:
1. A thermo-acoustic refrigeration system comprising:
a) An amplifier, which amplifies the sound wave (1)
b) A speaker, which produce sound (2)
c) A resonator / acrylic tube, in which the expansion and compression of sound waves occur (3)
d) A stack, divides the resonator into hold and cold regions (4)
e) A temperature indicator, which enables to read the temperature of hot and cold regions
digitally (5)
f. Thermocouples, to record the temperatures of hot and cold regions (6)
2. As per claim 1, an amplifier, a device that works by changing a small input signal to get an improvised output signal which is an amplified form of sound signal, is connected to the speaker
3. As per claim 1, the speaker, a device that produces sound in response to an electrical audio signal input is connected to one end of Resonator/ Acrylic tube
4. As per claim 1, the Resonator/Acrylic tube is made up of acrylics, which is a typical kind of transparent plastic material possessing excellent mechanical properties like strength and stiffness and also exhibit a good optical clarity
5. As per claim 1, the stack, a laminated plastic sheet is stacked in a spiral shape and placed inside the resonator / acrylic tube through which sound wave passes and pressure variation along with variation of temperature occurs due to it
6. As per claim 1, temperature on either side of the region is recorded by a temperature indicator
7. As per claim 1, thermocouples are placed on either side of the stack and are connected to temperature indicator to record temperature of hot and cold end , Description:Field of Invention
The present invention relates to improvement in thermo-acoustic refrigeration, in particular the stack employed in thermo-acoustic refrigeration system.
Background of the Invention
Thermo-acoustic refrigeration system utilizes sound waves for transferring heat. The sound waves compress and expand and interact with air around to cause fluctuations in pressure and in-turn temperature difference. As sound waves are compressed, they create a high pressure zone and releases heat. On the other hand, expansion of waves creates a low pressure zone and has a tendency to absorb heat. In an ordinary conversation, the temperature would fluctuate by 1/10000th of a degree. But with much higher volume, say 195 decibels, temperature can fluctuate enough to keep food frozen. A refrigerator keep things cool by using a device to transfer heat from food we store to a surface where heat is rejected, US6658862B2. Based on the fact that sound waves absorb and release heat, sound waves can be used as a means to remove heat from the refrigerator. In a thermo-acoustic freezer, gas transport sound waves that are released out of a large speaker into a cascade tube to create an acoustic wave. The wave oscillates back and forth between two enclosures, US5174130A. For heat to transfer more effectively, gas can be made to keep in contact with the solid and still maintaining the desired stable temperature. As and when the wave passes through cool surface, it usually expands and tends to absorb heat. Further, it traverse back carrying heat will also gradually compress, US5165243A. Sound waves release heat into heat sink effectively transferring heat away from the cool source. By repeating the process the system reduces temperature and so work as a refrigerator. To facilitate the extent of heat travel, to or from energizing solid, thermo-acoustic freezer uses solid with spaces called as a stack. The stack improves heat transfer rate as it intensifies the wave travelling from one end of solid to another end. The ideal thermodynamic working fluids for thermo-acoustic refrigeration systems are noble gases as these are non-toxic and environmentally acceptable.
Thermo-acoustic refrigeration system are known in the prior art. For instance US6688112B2 discloses thermo-acoustic refrigeration cycle and device using gas-vapour as working medium with dry stack of solid material. The desired temperature difference has been established using a standing wave between the regions of compression. Heat is observed transferring from the working medium to the stack. Also, CN103486778B discloses the use of stacked hot sound machine in thermo-acoustic technology being used as heat generator.
A thermoacoustic refrigeration equipment with low cost laminated sheets using a stack and importance of its position in the resonator.
Summary of the Invention
In the light of above mentioned thermo-acoustic refrigeration system, present invention aims to utilize laminated plastic sheet as a stack material in spiral shape through which sound waves passes and pressure variation along with variation of temperature occurs due to it.
The specific objective of the invention is to analyze temperature drop using plastic stack.
A further specific objective of the invention is to plot temperature distribution on cold and hot ends with respect to time.
Brief Description of Drawings
The invention will be described in detail with reference to the exemplary embodiments shown in the figures wherein:
Figure 1 Pictorial representation of experimental setup
Figure 2 Stack: thermo-acoustic refrigeration
Detailed Description of the Invention
The embodiments of present disclosure provide a thermo-acoustic refrigeration system designed based on the following criteria, i) Sound waves to pass through the resonator and ii) In-turn passes through the stack wherein pressure variation along with variation of temperature occurs.
From the past 50-60 years refrigeration and air conditioning industry has developed in a rapid manner and the growing demand has led to the expansion of several refrigeration and air conditioning based applications varying from domestic purpose refrigeration to advanced refrigeration technologies emerging in the modern world. Refrigeration and air conditioning systems play very crucial role in several heavy machinery and also in case of every scientific domain. All of the existing conventional refrigeration systems use refrigerant based VCR (Vapour Compression Refrigeration) systems to get any desirable temperature. In order to attain these temperatures various types of refrigerators are employed for usage so that the purpose of refrigeration is fulfilled. All conventional methods of refrigeration employ several eco-sensitive refrigerants. The HFC or CFC emissions produced out of these refrigerants may lead to certain hazardous effects which are major contributors in case of global warming and ozone depletion. The restriction on using CFC and uncertainty over replacing CFC paves a way to adapt thermoacoustic systems as they also show significant advantage than conventional refrigerators.
With reference to the figure 1, the “thermo-acoustic refrigeration system” is provided in accordance to an embodiment of the present disclosure. Sound waves undergo incident oscillations, displacement along with variation in pressure. To create thermoacoustic effect, the said oscillations should be produced very close to a solid surface. In TAR mode of refrigeration technique, loud speaker (Acoustic driver) generates sound waves, which acts as a pressure wave that oscillates to and fro in order to compresses the working medium (unpressurised air) and also it creates interaction between pressure and temperature oscillations. The interaction of pressure and temperature oscillations initiates compression and expansion phenomenon of the working medium in further period of time interval. Then after this, working medium moves through the small gaps of stack to produce desirable temperature gradient leading to a feasible refrigeration effect.
An Amplifier (1), a device that works by changing a small input signal to get an improvised output signal which is an amplified form of sound signal. Amplifier in this case is used to enhance the sound input produced by the acoustic driver, the basic objective of using an amplifier is used to control the frequency of the sound (produced from acoustic driver), is connected to the Loudspeaker (2). The loudspeaker, a device that produces sound in response to an electrical audio signal input is connected to one end of Resonator/ Acrylic tube (3), which serves the purpose of producing sound energy in the waveform which helps in determining the parameters such as displacement acceleration and frequency of the sound waves through which the amplified sound wave passes into it. The stack (4), a laminated plastic sheet is stacked in a spiral shape and placed inside the resonator / acrylic tube through which sound wave passes and pressure variation along with variation of temperature occurs due to it. It has less conductance to heat and an appreciable heat carrying capacity to attain constant temperature gradients. It is placed inside the resonance tube at a particular position. The stack divides resonator into two regions, cold and hot regions.
The Resonator/Acrylic tube (3) is made up of acrylics, which is a typical kind of transparent plastic material possessing excellent mechanical properties like strength and stiffness and also exhibit a good optical clarity. The acrylic tube is connected to the loudspeaker through which sound waves pass. The extreme end of a resonance tube is closed with insulation (like thermocol). The acoustic driver (loud speaker) connected to the resonator which further accommodates a spiral stack inside it located at a region nearer to the acoustic driver. The dimensional specifications of acrylic tube play a very crucial role during the operation of TAR system. Specifications: length = 600mm, Internal diameter = 100mm, Outer diameter = 110 mm, Thickness = 5mm. The amplified sound wave inside the resonator vibrates and expansion and compression take place on either side of stack. Compression region is hot and expansion region is cold region. Temperature on either side of the region is recorded by a temperature indicator (5). Thermocouples (6) are placed on either side of the stack and are connected to temperature indicator to record temperature of hot and cold end. Time taken to measure each reading is according to the experiment.
The TAR consists of an amplifier which amplifies the sound waves that are connected to the loudspeaker and the resonator through which the amplified sound waves pass from one end to other end. Inside the resonator, a stack is placed which divides the resonator into two regions. The amplified sound wave inside the resonator vibrates and expansion and compression takes place on either side of the stack, the compression region is the hot region and the expansion region is the cold region. The temperatures on either side of the region are determined by temperature indicator, thermocouples are placed on the either side of the stack and are connected to the indicator. The time taken to measure each reading is recorded according to the experiment. When a gas oscillation is sent the tube by the loudspeaker, the gas packet (unpressurised air) expands due to propagation of sound and subsequently its temperature drops. The gas then absorbs heat from the stack surface. This produces a temperature drop in the low-pressure region. Then as the gas packet moves to the high-pressure region, the gas temperature rises, and it stops absorbing heat from the stack. This heat is then removed from the tube, creating the thermos acoustic cycle.
7 Claims & 2 Figures

Equivalents
The thermo-acoustic refrigeration system of the present invention discloses its usage in terms of attaining lower temperature using sound waves. The same machine/operation/mechanism may be used in air-conditioning unit as-well. The scope of the invention is not limited to its usage as thermo-acoustic refrigeration system.