System-CoolAC. Bharatividyapeeth College of Engineering, Deekshant Bharti Scholar, New Delhi, India

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1 A Novel Design of Low Cost Domestic Cooling System-CoolAC Abhishek Gandhar Associate Prof., Deekshant Bharti Aditya Jain Shiv Wadhwa of Engineering NewDelhi, India Rahul Kumar mehta Abstract This paper presents an idea to design a new and innovative cooling system using design merits of both, an air conditioner and a desert cooler. The coolac has been designed for optimal utilization of electric energy and providing maximum cooling. The idea goals toward emanating the growing power consumption for cooling by providing the same in most efficient way. According to an estimate, world energy demand will grow by 56% in between [1]. Hence, besides executing the desired cooling within its limit, the operation should be frugal too. Thus, implementing this idea may aid solving the problem of ever increasing demand of energy. Keywords Cooling; Honeycomb; Evaporative; Refrigerent; Wet bulb temperature; Dry bulb temperature. I. INTRODUCTION This design combines the merits of two widely used domestic cooling systems namely, a desert cooler and an air conditioner. The efficiency of evaporative cooling, as in a desert cooler, combines with recirculation of filtered and cooled air, as in an air conditioner, to make the coolac more efficient and effective the present systems. Not only the merits are combined, demerits of both systems are eliminated. Low cooling capability of desert cooler makes it unfit for high cooling requirements. While on the other hand high power requirement of an air conditioner and use of refrigerant gases makes it less eco-friendly. These demerits of present cooling systems will be eliminated with coolac. II. BACKGROUND To understand coolac, a brief review of the present cooling systems is necessary. Three widely used domestic cooling systems are mentioned below - A. A Fan A fan is a device used to create a flow within a fluid, typically a gas such as air. There had been much advancement in design of fan like being operated by hand in earlier days to large electric fans in present world. However, a fan is not a cooling device itself. The effect of cooling is felt due to evaporation of moisture present on one s body. Air flow created by a fan just facilitates the evaporating process. B. A Desert Cooler Evaporative cooling is the natural way of cooling, felt when standing in breeze wearing wet clothes on a hot sunny day. The moisture present in the clothes absorbs the heat to evaporate and leaves a cooling effect. An evaporative or desert cooler cools the air by means of evaporation of water. The chemical change, water converting to vapour, requires a particular amount of heat, called the latent heat. This heat comes from surrounding air and water. The heat is absorbed and removed leaving a cooling effect behind [2]. Generally wood wool pads, as shown in fig. 2, are used in coolers to hold water. A water pump is used to continuously supply water to pads. Water evaporates from pads, lowering their temperature. An axial fan creates flow of fresh air from outside environment over the pads and throws the cooled air in the house. Since air coolers sucks air from outside, the house to be cooled should be well ventilated to facilitate cross ventilation. While understanding the operation an air cooler, one must also be aware of dry bulb temperature and wet bulb temperature. Dry bulb temperature is just another term used to define air temperature or temperature measured by a thermometer exposed to air but shielded from moisture and radiation. Wet bulb temperature refers to adiabatic saturation temperature which is generally lower than dry bulb temperature on any given day and time. It is the temperature measured by thermometer when its bulb is covered with wet muslin cloth and is kept in air under sun. Higher the humidity content in air, lower the difference between dry and wet bulb temperature as evaporation is reduced when air contains more water vapours [3]. Wet bulb temperature is ideally the minimum attainable temperature by evaporative cooling. Evaporative coolers are power efficient and this makes it a low cost option for optimal cooling. Relative humidity content in the cooled air is much higher than the input air, making people feel of stickiness inside the house. However, as evaporation of water is necessary for air cooler to work, /16/$ IEEE

A Novel Design of Low Cost Domestic Cooling System-CoolAC 283 evaporative air coolers are ineffective in areas having high humidity content in air.

Hot refrigerant cools down and rejects more heat as it condenses again to cool liquid refrigerant which flows into the evaporator to repeat the process, thus creating a refrigerant cycle.

thing should be noted here that the two air flows, one over evaporator and one over condenser are thermally insulated from each other.

2 A Novel Design of Low Cost Domestic Cooling System-CoolAC 283 evaporative air coolers are ineffective in areas having high humidity content in air. Now, the hot gaseous refrigerant enters the condenser. Condenser also has copper or aluminum coils through which hot refrigerant flows. An exhaust fan creates an air flow over condenser coil. Hot refrigerant cools down and rejects more heat as it condenses again to cool liquid refrigerant which flows into the evaporator to repeat the process, thus creating a refrigerant cycle. Air flow takes the rejected heat along with it and dissipates into the atmosphere. thing should be noted here that the two air flows, one over evaporator and one over condenser are thermally insulated from each other. Some other components like expansion valve, temperature sensor are also shown in fig. 3. Fig. 1 Working of Evaporative Cooler To understand the working of an AC in details, one may refer to the video link given in reference [6]. As air conditioner recirculates air inside the room again and again, it is effective only when operated in a closed space, unlike air cooler. Use of compressor makes AC a high power consuming device. Both the initial and operating costs of an AC are very high compared to that of cooler. Also, refrigerant used is Freon gas, which is harmful for ozone layer. Thus, operation of air conditioner causes harm to environment. Fig. 2 Wood Wool Evaporative Pad C. An Air Conditioner The modern form of Air Conditioner or AC was invented by an electrical engineer named Willis Haviland Carrier back in 1902[4]. Again, principle used for cooling is evaporation, but a bit different. An AC uses a cooling media called refrigerant, typically a gas (at room temperature) instead of water. The machine has generally three parts namely, evaporator, condenser and condenser. The refrigerant gas flows from one part to another, continuously switching its state between gas and liquid, absorbing heat from inside of room and dumping it outside. Evaporator is placed inside the house while condenser is placed outside. Compressor is located between the other two. In simple terms working of a general domestic AC can be explained as follows. Liquid refrigerant (below room temperature) is made to flow through the copper coils in evaporator. As the name suggests, liquid refrigerant evaporates into gas in evaporator. This happens because air is sucked from room using a centrifugal blower/fan and made to flow over evaporator coils. Liquid refrigerant absorbs the heat from air and evaporates, leaving the chilled air over evaporator which is thrown back into the room. Refrigerant in gaseous state heads towards compressor. Compressor, as the name suggests, compresses the refrigerant without changing its state back to liquid. According to Gas Laws, when pressure of a gas is increased holding its volume constant, temperature of gas increases. With symbols having their usual meaning, combined gas law is formulated as, Fig. 3 Working of Air Conditioner III. COOLAC THE NEW DESIGN As stated before, the coolac draws its design by combining the merits and eliminating the demerits of its predecessors. Efficiency of evaporative cooling (using water) combined with effectiveness of AC due to recirculation of air inside room gives optimal cooling. This helps to keep humidity inside room under control. Also, electric power requirement is reduced drastically as compressor is removed from cooling cycle. A. Components from Evaporative Cooler Evaporative Pads Honeycomb pads are used in coolac instead of wood wool pads used in air coolers. As the name suggests, honeycomb pads resembles the hexagonal geometry of honeycomb created by honey bees. They provide larger surface area for water to evaporate and have much longer life than wood wool pads. Efficiency of honeycomb pads is approximately 85%, 10% more than wood wool pads [7].

284 Innovative Applications of Computational Intelligence on Power, Energy and Controls with their Impact on Humanity (CIPECH-16) Fig. 6 Centrifugal Blower Fig.

Although the same process occurs in coolac, but it aims to make water itself cool. However, as an outcome of process, both air and water are cooled.

A pump having rating 40W is used in coolac. B. Components from Air Conditioner Evaporator Copper coils used as evaporator in air conditioner is used as cooling coil in coolac.

3 284 Innovative Applications of Computational Intelligence on Power, Energy and Controls with their Impact on Humanity (CIPECH-16) Fig. 6 Centrifugal Blower Fig. 4 Honeycomb Pad Water as Cooling Medium Main energy saving and eco-friendly component from air cooler is used as cooling medium in coolac. Water is used in cooler to make air cool. Although the same process occurs in coolac, but it aims to make water itself cool. However, as an outcome of process, both air and water are cooled. Water Pump In air cooler, pump is used to supply water from tank to pads. In coolac, water is first passed through cooling coil and is then supplied to pads. A pump having rating 40W is used in coolac. B. Components from Air Conditioner Evaporator Copper coils used as evaporator in air conditioner is used as cooling coil in coolac. Chilled water from tank will be passed through coil to lower the coil temperature. Low temperature of coil translates into lower air temperature of room. CoolAC also recirculates air inside the room as an air conditioner does. This helps in increasing effectiveness while keeping humidity under control. C. Modelling & Working A simple layout of coolac is shown in fig. 7. As explained before, coolac uses thermal insulation, like air conditioner, to keep heat source and heat sink isolated. To understand working, one must start from water dropping over evaporative pads. As water drips downwards (due to gravity), a part of it evaporates, making the water left cooler. An axial fan increases the evaporation rate. Cooled water collected in tank is passed through cooling coils using water pump making coils cool. Heat transfer takes place from copper to water. Water losses its heat again while dripping over pads. A centrifugal blower sucks air from room creating flow of air over cooling coils. Now heat is transferred from air to copper, making air cool. Cooled air is thrown back into the room. Heat absorbed by copper is again transferred to water, when more of it comes. Fig. 7 2D layout of CoolAC Fig. 5 Copper cooling coil Centrifugal Blower and Axial Fan A blower & a fan coupled to a single 1-phase induction motor has been inherited by coolac from air conditioner. Blower sucks air over cooling coils and throws it back in room. On the other hand, fan is blower s outdoor counterpart. It throws the air over evaporative pads to increase evaporation of water. Difference between blower and fan is that the difference in direction of input & output air is 90ᵒ in blower while having no difference in case of fan.

A Novel Design of Low Cost Domestic Cooling System-CoolAC 285 Fig.

Also, as there is no direct contact between indoor air and water, there is no means by which moisture content in indoor air may increase.

However, as cooling principle and process is similar to that of an air cooler, any temperature below wet bulb temperature is not attainable with coolac. D.

4 A Novel Design of Low Cost Domestic Cooling System-CoolAC 285 Fig. 8 3D layout of CoolAC As the air inside room is circulated again & again over the cooling coils, coolac is designed to be more effective than an evaporative cooler. Also, as there is no direct contact between indoor air and water, there is no means by which moisture content in indoor air may increase. With absence of any compressor and refrigerant cycle, power consumption is much less than that of an air conditioner. However, as cooling principle and process is similar to that of an air cooler, any temperature below wet bulb temperature is not attainable with coolac. D. CoolAC Photgraphs Actual model and design of coolac is shown in figures Fig. 9 shows the side view while backside of coolac can be seen in Fig. 10. Fig. 10 depicts design of coolac completely Fig. 10 CoolAC Fig CoolAC IV. OBSERVATIONS & COMPARISON CoolAC was tested by a temperature and humidity sensor module having specifications as follows Temperature Range = -50 to 70ᵒC Relative Humidity Range = 20% to 99% Resolution of temperature sensor = 0.1ᵒC Resolution of humidity sensor = 1% Fig. 9 CoolAC Accuracy of temperature sensor = +/- 1ᵒ Accuracy of humidity sensor = +/- 5% Dimensions of room in which coolac was tested Length = 6.23 feet = cm Breadth = 3.86 feet = cm Height = 7.08 feet = cm After testing coolac, following observations were noted. Observations were made on the day when wet bulb temperature was noted to be 20ᵒC. A. CoolAC Parameters Total power consumption = 340 W Power required by induction motor = 300 W

5 286 Innovative Applications of Computational Intelligence on Power, Energy and Controls with their Impact on Humanity (CIPECH-16) Power required by water pump = 40 W Rated current (at 230 volts) = 1.6 A Power factor = 0.92 lagging Centrifugal blower diameter = 22 cm Axial fan = 40 cm CoolAC length = 2.15 feet = 65.7 cm CoolAC Breadth = 2.15 feet = 65.7 cm CoolAC Height = 2.78 feet = 84.8 cm A comparison here may be drawn with air conditioner having power rating between 1.4 KW & 1.6 KW of 1.5 ton AC. Power consumption increases with increases in cooling capacity. B. Water Temperature Temperature of water was noted 29ᵒC while filling water tank. However, after 30 minutes of operation, temperature of water dropping on pads was noted to be 23ᵒC while that of leaving the pads was 20ᵒC. Thus, after evaporation, temperature of water dropped by 3ᵒ. After 30 minutes, temperature of water stopped dropping. It means saturation was achieved by water in 30 minutes. Since the principle and process of evaporation is same in coolac and evaporative cooler, minimum temperature attained by water on any given day is equal in both systems. C. Air Temperature Indoor Temperature of room in which coolac was tested was noted to be 34.5ᵒC. Outdoor temperature stood a bit higher at 39.3ᵒC. Since coolac sucks air from room itself, it can be inferred that intake air temperature was 34.5ᵒC. After 10 minutes from starting, temperature of output air was measured to be 32ᵒC. 25 minutes from starting, 30.2ᵒC. 40 minutes from starting, 29.5ᵒC. 50 minutes from starting, 28.7ᵒC. 60 minutes from starting, 27.6ᵒC. As it can be seen clearly, there was a considerable drop in indoor air temperature. However, after first hour of operation room temperature dropped to 31.6ᵒC D. Indoor Moisture Content Relative moisture was measured to be 30% at time of starting coolac. Relative moisture rose to 37% after 1 hour of operation. A note should be made here that it is the relative humidity content that increased not the actual moisture content. As air inside the room cools down, its capacity to hold moisture decreases, which is reflected by increased level of relative humidity. An evaporative cooler increases the actual humidity content of air by 25-30%. On the other hand, an air conditioner decreases moisture content considerably inside the room. E. Comparison Table I shows basic comparison between air conditioner, coolac & air cooler on various parameters. Parameters Power Requirement Ventilation required Recirculation of air inside room Humidity inside room Type of pads Number of fans Cooling Capacity Initial and operating cost Cooling medium used Compressor Required Environmental impacts TABLE I. Air Conditioner COMPARISON TABLE Cooling Systems CoolAC Air Cooler High Low Lower No No Yes Yes Yes No Decreases No change Increases Not required centrifugal blower and one axial exhaust fan Honeycomb pads centrifugal blower and one axial exhaust fan Wood wool pads Axial exhaust fan Higher High Low High Low Low Freon gas Water Water Yes No No Harmful for nature V. CONCLUSION Eco - friendly Eco - friendly CoolAC, combining advantages of both an AC and an evaporative cooler, it may become an option with other two to choose from in future. Although, the cooling capacity of coolac cannot be compared to that of an air conditioner, but still a trade-off can be made between power requirement and cooling capacity. Power requirement of coolac & an evaporative cooler is comparable, so coolac can emerge as better option in terms of cooling capacity. CoolAC possesses some features which are listed as follows Low capital & operating cost Water used for cooling Environment friendly Good cooling capacity Clean & filtered air inside room REFERENCES [1] [1] eia.gov-todayinenergy eia.gov-todayinenergy [2] [2] evaporativecooling-principle [3] [4] howstuffworks.com/ac.htm [3] [4] howstuffworks.com/ac.htm [5] [5] [6] [7] [6] [7] difference-between-aspen-pads-and-rigid-media-pad

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