Design of HVAC System using the Phenomena of Diurnal Temperature fluctuation

The total energy usage of the domestic sector accounts for 35.3% of total global energy consumption of this percentage, 50% is used for room and domestic HVAC systems. We worked for designing a standard module to achieve the maximum temperature difference. In this paper Diurnal Temperature Variation phenomena has been studied. The standard Simulation of the HVAC system using Diurnal Temperature Variation has been performed. The current work is a scale down model of Ground Source Heat Pump which is totally renewable in nature. This scale down model works on Diurnal temperature variation. Diurnal temperature fluctuation is the temperature difference obtained during the daytime and night time with higher and lower soil temperature. Same phenomenon is used to obtain a cooling effect and heating effect as we go deeper inside the Earth. The current work is complete replica of Ground source heat pump where the application of this phenomenon is used. Air as a flowing media is used for heat transfer between soil. The air is meant to be flown through the capillary tubes and at certain depth we get a cooling or heating effect according to atmospheric conditions. Along with that we do have to care about the human leisure requirements, for the very purpose we are also passing some amount of fresh air along with reusing the cool air inside the room by flowing it through the walls of room to provide insulation against the infiltrating heat and other elements that add temperature inside the room. It has been identified the 10.40% reduction in atmospheric air and hence it can be concluded that the geothermal HVAC system can be a sustainable and energy efficient alternative to traditional HVAC system. Also identified that the geothermal HVAC systems offer a promising solution for reducing greenhouse gas emissions and increasing energy efficiency in the building sector.


Introduction:
The term HVAC stands for "Heating Ventilation and Air Conditioning" and is commonly associated with the heating and cooling Industry.It is a system that performs three major functions, Heating, Cooling, and Ventilation of air generally used in residential, commercial, or Industrial Buildings.There are two types of ventilation systems: natural and mechanical.Natural ventilation relies on the natural movement of air through windows, doors, and other openings in the building.Mechanical ventilation, on the other hand, uses fans and ductwork to circulate air throughout the building.Mechanical ventilation systems can be further categorized as either exhaust or supply systems [1].The three main functions of an HVAC system are interrelated, especially when providing acceptable indoor air 1285 (2024) 012006 IOP Publishing doi:10.1088/1755-1315/1285/1/012006 2 quality and thermal comfort.Your heating and air conditioning system is often one of the most complicated and extensive systems in your home, but when it stops working you'll know soon enough!There are nine parts to your HVAC system that you should be familiar with, the air return, filter, exhaust outlets, ducts, electrical elements, outdoor unit, compressor, coils and blower.One of the primary sources of heat in a room is the sun.Sunlight enters through windows and warms up the air and objects in the room [4].This is why rooms that face south or west tend to be warmer during the day, as they receive more direct sunlight.Finally, heating systems can add heat to a room.In colder climates, homes and buildings are often equipped with heating systems, such as furnaces or heat pumps, which add heat to the air and distribute it through the ductwork or radiators.In summary, heat is added to a room through various sources, such as sunlight, human activities, electrical devices, and heating systems.These sources increase the temperature of the air in the room, which can make us feel hot and uncomfortable.Now in order to remove this heat there are special parameters and processes which are taken into account.To make a room cooler and adaptive to human comfort conditions we use the Conventional HVAC system which has a Compressor, condenser and all the major component to allow the exchange of heat from hot input reservoir to cold reservoir.Amongst which the natural and efficient one is the Natural Convective Heat transfer mode, in simple terms, Ventilation [5].Ventilation is an essential component of HVAC systems and can help to reduce the temperature of a room by removing hot air and replacing it with cooler, fresher air.Ventilation works by circulating air through a building, either mechanically or through natural means, and can help to remove heat, moisture, and pollutants from the indoor environment.In a mechanical ventilation system, fans or blowers are used to circulate air through the building.The air is typically drawn in through vents or ducts and is filtered to remove pollutants before it is distributed throughout the building.In addition to providing fresh air, mechanical ventilation systems can also be used to extract hot air and moisture from the building, which can help to reduce the temperature and humidity levels [7].Natural ventilation systems rely on natural airflow to circulate air through the building.This can be achieved through the use of windows, vents, or other openings that allow air to enter and exit the building.Natural ventilation can be particularly effective in moderate climates, where outside temperatures are similar to indoor temperatures and natural airflow can help to maintain a comfortable indoor environment.In addition to ventilation, HVAC systems can also include air conditioning, which is a powerful tool for reducing the temperature of a room.Air conditioning works by removing heat from the air and transferring it outside the building, which helps to cool the indoor environment.Air conditioning systems can be designed to cool individual rooms or entire buildings, depending on the needs of the occupants.Similarly, Air conditioning systems work by removing heat and moisture from indoor air, and then cooling and dehumidifying the air before circulating it back into the room.The process of air conditioning involves several key components, including the refrigerant, compressor, evaporator, and condenser.First, the refrigerant, a special fluid that absorbs and releases heat as it circulates through the system, is compressed by the compressor, which increases its temperature and pressure.The hot, high-pressure refrigerant then flows to the condenser, where it releases heat to the outside air, typically through a set of metal fins or coils [11].This causes the refrigerant to cool and condense into a liquid.Next, the liquid refrigerant flows through the expansion valve or metering device, which reduces its pressure and temperature.This causes the refrigerant to evaporate and absorb heat from the indoor air as it passes over the evaporator coils.The now-cooled and dehumidified air is then circulated back into the room by a fan or blower.The process of evaporation and condensation continues as the refrigerant cycles through the system, continuously removing heat and moisture from the indoor air and transferring it to the outside environment.The thermostat controls the temperature of the indoor air by turning the air conditioner on or off as needed to maintain the desired temperature setting.Overall, air conditioning systems reduce the temperature of a room by removing heat and moisture from the indoor air and transferring it to the outside environment.This is achieved through a combination of compression, condensation, evaporation, and expansion of the refrigerant, which causes the indoor air to be cooled and dehumidified before it is circulated back into the room.The problem statement which we have selected is to replace or add renewable sources to decrease the consumption of electricity.Our purpose is to make an ideal & stand-alone HVAC system using the phenomenon of diurnal temperature fluctuations.The objectives of present study are i) To decrease Dependence on Conventional ways of HVAC ii) To decrease the load on the conventional systems and try to eliminate it iii) To study these temperature phenomena for different terrain iv) To decrease the emission caused by conventional systems v) To try to make the HVAC systems source renewable.

LITERATURE SURVEY
The relevant published literature has been review for the present work and its details are provided below.

S.N. Title
Author Finding 1 A Review of the Advancements in Geothermal Heating and Cooling System Nimish Dhepe, et al. 2017 In this review paper, the authors discussed the use of closedloop refrigerant systems to improve conventional HVAC systems.They also demonstrated the importance of HVAC systems and its power consumption.This paper, considered the application of adding nano fluids to water to improve its performance.They experimented with base liquids (water and his EG) containing different types of nanomaterials.They succeeded in increasing the thermal conductivity of the liquid and also analyzed the pressure drop within the liquid.The results were promising, showing a significant increase in heat transfer performance of fluid.In this paper a strong interaction between the effectiveness of two heat exchangers was found as the water flow rate varies.5

Design of HVAC System
In the present work, a demonstration of the Diurnal fluctuation phenomenon designed to get the desired room temperature for having a Cooling and Heating effect as per human requirements.A demonstration of Earth's underground temperature differences is depicted using a rectangular box of some height filled with 80% of its volumetric capacity with three different types of soil namely; Red soil, Black soil, and Laterite soil (regionally: Murum Soil).One soil is used at a time at the very first instance to record the heat convection rate of the soil so that we shall get an idea of which soil stays responsible for the maximum temperature difference [6].For this very purpose, the current work depicts the actual working of a Geo-thermal heat exchanger and its types.For this current work, we are using an Open Loop system where the air is used as a conduction media for heat conduction and reduction [7].

Current work:
Design of HVAC system using Di-urnal temperature fluctuation phenomenon [1].According to the literature survey on the geothermal HVAC system and diurnal temperature variation, it is possible to design a Heat Exchanger, which can solely run on the Earth's temperature differences.So far as the experiment regarding heat convection rate is concerned, we have experimented and have data that there exist some temperature changes as we go deep down the earth [6].Our current work depicts the same Scale down model of the actual HVAC system used in European or American Countries The current work is a full Wooden box containing 90% of its volumetric capacity as Omnibus soil or well-known our Red Soil.Now before considering this soil as our current work soil we checked the heat convection parameter of every soil available in our locality.The most flared one was 1. Red Soil 2. Black Soil

Laterite Soil
Among all these three, the highest heat convection rate soil shall be eliminated and the one where heat penetration inside is very low shall be considered.For this very purpose we performed an experiment on our behalf to select a well-deserved soil to meet our current work requirement.The data that coincided with our demand for a well versed less heat convective soil was RED SOIL itself.Further on with more literature study over libraries, Internet and Research paper we came to know the most reliable and adequate soil which should be used shall be soil.[11] Once the selection of soil is done, arrangements are made so that proper circulation of heat-carrying media can be done; here "Air".There is a blower attached at the inlet of the "Capillary tube" and the capillary tube is meant to circulate all over the area in a sinusoidal form [6].The blower sucks the air from the atmosphere where the filter attached to it cleans the heavy particles of dust, and garbage inside it.The heat inside it has a certain amount of Thermal energy.To make it cool we have to lose this thermal energy to certain other media with temperature variance, therefore, this air is made run through capillary tubes, which are buried inside the soil.Due to diurnal change, if the atmosphere temperature is high the ground temperature shall be less and vice versa [1] Rejection of thermal energy from the air to the soil will take place and cool air is now ready to take an exit from the Capillary pipes.The pump is a kind of trampoline platform, elevating the flow of air into the room.Once the air is supplied to the room, one can have the desired cooling effect and better ventilation, without AC, cooler, fan, or any traditional methods of cooling [1] If we are concerned with only the cooling part, above mentioned steps are versatile and are pioneers of the current work.However, we need to meet the human requirements as well, only circulation of filtered air inside the room every time with a continuous process can make the situation worse for living over the time of usage.For this one more inlet is provided in the room for fresh air circulation, however, as we don't want to disturb the cooling of the room, we keep this to its optimum levels only.This scaled-down model is inspired by the geothermal heat ventilation system from the western regions.Implementation of this on a large scale can lead to less electricity consumption, which reduces the use of Fossil fuels and in return result betterment of Earth only.

Design of Heat Exchanger using Fusion 360
Fusion 360 is cloud-based 3D CAD/CAM software developed by Autodesk.It is an all-in-one solution that offers design, engineering, and manufacturing tools for product development.The software is popular among hobbyists, makers, engineers, and designers, as it provides a comprehensive set of features that allow users to create complex designs and bring their ideas to life.The user interface of Fusion 360 is intuitive and user-friendly, making it easy for new users to get started.The software uses a timeline-based workflow that allows users to make changes to their designs at any stage of the process.Fusion 360 supports both parametric and direct modelling, which means that users can make precise changes to their designs or make quick modifications on the fly.One of the key features of Fusion 360 is its collaboration tools.The software allows multiple users to work on the same current work simultaneously, making it ideal for teams or individuals who work in a collaborative environment.Fusion 360 also offers a range of cloud-based services, including data management, current work management, and collaboration tools.
Fusion 360 includes a range of tools for design, including sketching, sculpting, and T-spline modelling.The software also offers a range of analysis tools, including stress analysis, thermal analysis, and flow simulation.These tools allow users to test and validate their designs before they are manufactured.Fusion 360 also includes a range of tools for manufacturing, including CAM tools for CNC machining, 3D printing, and additive manufacturing.The software also offers tools for generating tool paths and G-code, making it easy to generate the instructions needed to produce a physical product.

Figure 1.Design model of system
Now above mentioned is the Design of our scale down model, which is being prepared in Fusion 360 for the manufacturing process.The model comprises of an iron frame, which is the base of our current work.A wooden box, which is mounted on the iron frame, and red soil, which is filled inside the wooden box as an Earth demonstration.The iron frame used is made up of SS material.The iron in the form of square pipes is used to add more rigidity and strength to the overall structure of our current work.The square pipes are fused together using Arc wielding method to provide a strong joint to the overall joints present inside the frame.Iron of SS material is heavy, strong, economically reliable and quite durable to sustain the weight of overall current work structure.Not shown in the design but, the structure is made mobile using wheels, 4 wheels which are attached to end face of each square pipe are used to make current work more mobile and flexible for movement.
Design shows usage of acrylic sheet for the manufacture of soil container but due to cost barrier, we have to shift to development of wooden box.The Plywood is used to make the box, which shall contain the red soil of 90% of its volumetric capacity.Furthermore, the wood has to be reluctant to moisture and water coming from soil.Usually wood undergo certain deforms like, Absorption of water, Dimensional Changes, Strength Reduction, Decay and rot, etc.To avoid such deformations we have added 3 consecutive layers of primer to protect the ply-wood from impacts of water exposure, additionally, 2 layers of black paint is being applied a 5 layer protective shield is prepared on each side of box to keep the wood free from water exposure.There is another component which is not shown in the design.The component is the passage way for our outside air circulating from atmosphere to the room.This one is namely, Copper capillary tube.This tube of minute diameter is being placed in between the box, the tube is just at the center of the box which is sandwiched between two layers of soil.After pouring the first layer of the soil, we placed Copper tube and then we added the second layer so as to perform the heat transfer.Further coming, in order to record the temperature changes occurring in the atmosphere, inside the soil, and inside the room, we add a data logger which is responsible to collect data every 10 seconds after its activation.The data logger, which is developed by students, uses 4 temperature sensors to record the data.One of the temperature sensors is exposed to an open atmosphere while others too are kept inside the room and inside the soil respectively.The brain of this data logger i s an Arduino board that processes the data and is shown in the Arduino IDE Interpreter.
Our room, which is to be ventilated, is made up of foam sheet and Acrylic sheet.The first face of the room is kept transparent so as to see inside the room.Adding on to an Air pump, it draws air from atmosphere and circulates it from the copper tube to the room for ventilation Below mentioned are the dimensions and materials used to make the structure of each component.In order to find out the effectiveness and the temperature difference from inlet of the pump to the outlet, we need to find some parameters that can fit our formula.For this purpose the use of Zeta-NTU method was used.The Zeta NTU method, also known as the Zeta method or Zeta correction method, is a technique used to estimate the performance of heat exchangers.It is based on the effectiveness-NTU (Number of Transfer Units) method, which is commonly used to analyse heat transfer in such devices.The Zeta NTU method incorporates an additional correction factor, called Zeta (ζ), to account for the deviation between the actual heat exchanger performance and the performance predicted by the effectiveness-NTU method [12].This correction factor is introduced to compensate for non-idealities in the heat exchanger, such as temperature cross-flows, non-uniform fluid distribution, or flow maldistribution.The basic principle of the Zeta NTU method is to determine the effectiveness (ε) and NTU values for a heat exchanger using traditional methods, and then apply the Zeta correction factor to obtain a more accurate prediction of the heat exchanger performance.The corrected effectiveness (ε') is calculated as the product of the original effectiveness and the Zeta factor: ε' = ε × ζ.Now to calculate the outlet temperature after the heat transfer happening inside the soil, we can use, 1. Simplified heat transfer calculation for a specific scenario [12]: Where, Tair,out -Temperature of air leaving the coil Tair,in -Temperature of air at inlet, Tsoil -Temperature of soil.
ζ-Coefficient used to describe the relationship between the temperature difference and the heat transfer rate.Effectiveness (ε) of a heat exchanger [12]: The equation is related to the effectiveness (ζ) of a heat exchanger Where: ζrepresents the effectiveness of the heat exchanger, 'NTU' represents the Number of Transfer Units, which is a dimensionless parameter that characterizes the heat transfer capability of the exchanger, and 'e' is the base of the natural logarithm (approximately 2.71828).Furthermore, the Non-transferable Units were calculated using Formula, Non-transferable Units: In this equation: Cair is the heat capacity rate of the air with the smaller heat capacity (Cmin).It is the heat capacity of the fluid per unit time and temperature change.
The capacity of the air was a unknown factor therefore, Expression of the conservation of energy [12]: The equation here, Cair = Cp dm/dt is an expression of the conservation of energy.If we break this down we get: Total Resistance in system involving air, a tube, and soil [12]: 1/UA: This term represents the inverse of the overall heat transfer coefficient (UA) for the system.
Equation of Thermal Resistances of Air, Soil and Tube [12]: Rtube = ln {Do /Di } / 2 π λtubeL ( 7) The equation relates to the thermal resistance (Rair) of a system.Let's break it down: Rair represents the thermal resistance of the system.It is a measure of how difficult it is for heat to transfer through the system.h is the convective heat transfer coefficient, which represents the ability of the fluid (such as air) to transfer heat.Di represents the inside diameter of system.L represents the length of the system.Nu is the Nusselt number, which is a dimensionless parameter used in convective heat transfer calculations.
λair represents the thermal conductivity of air.Πl is the perimeter of the system.The equation Rair = 1/hπDiL = 1/Nu λair Πl indicates that the thermal resistance of the system is equal to the reciprocal of the convective heat transfer coefficient multiplied by the inside diameter of the system and its length.It is also equal to the reciprocal of the Nusselt number multiplied by the thermal conductivity of air and the perimeter of the system.This equation is commonly used in heat transfer calculations, particularly in situations where convective heat transfer is involved, such as in heat exchangers or cooling systems.It helps determine the resistance to heat flow and allows for the analysis of thermal behavior in a given system.With the help of these formulas, we were able to find the effectiveness, Length of the coil to be used and the outlet temperature coming out from the tube after the Heat exchange to the soil.Our effectiveness after Calculations were demonstrated as 0.97≈ 97%, this means, our effectiveness obtained after calculations using dimensions from table 3.1 are estimated to be 97%.With these parameters, we are ready to confront ourselves towards manufacturing of our Earth -Air Heat Exchanger.[2]

Experimental Methodology
We begin with manufacture of our Experimental current work whose sole purpose was to identify the best suited soil for our experiment.There were 3 types of soil found in large proportions in our locality, Red soil, Black soil, and Laterite soil (regionally: Murum Soil).
One soil is used at a time at the very first instance to record the heat convection rate of the soil so that we shall get an idea of which soil stays responsible for the maximum temperature difference.
The experiment Components used are as follows: The wooden box mentioned in the components is a closed system where it can contain the soil and whatever heat transmission is inside.The 4-side closed wooden box is pierced few holes for air ventilation and wire passage for the bulb and the data logger temperature sensor wires.The 100W bulb transmits heat of 6000J that is 6 KJ/min of heat is being transferred by the bulb into the closed environment of the system.In addition, aluminum foils are used to increase the effect of heating and concentrate it in the ambient part of the closed system.The sensors and the Micro-controller unit will record the data of their initial position and it will be stored.The cycle repeats every 10 seconds recording the temperature change of each temperature sensor.The temperature change is in descending form when read from the top and increases when read from the bottom.This data is recorded in three soils which were mentioned above.The highest convection rate; meaning, the highest rate of temperature transfer from top to bottom, that soil will be excluded to be used in the current work.We need Soil that will have a low convection rate where the bulb's heat is not convected much towards the bottom of the container.All three soil data are to be compared with the help of a temperature-time graph where the depth is already recorded by the position of a single temperature sensor at a specific depth of the container.and its constant temperature holding properties.This data logger is a universal device that will record the data and store it somewhere on the hardware.Initially purchasing a Data Logger would cost more than 10,000INR but as we manufactured it was a lot cheaper.
The data logger we prepared is a multi-temperature sensor data logger, which takes input from 4 temperature sensors and records it on the SD card module.The major work of this is to record the temperature and store it on the micro-SD card fed to the SD card module.The major component responsible to perform these actions is Arduino UNO with ATMEGA 320P.This is an open-source micro-controller board with a 14 digital pin input and output.Input is taken from the temperature sensors and is processed inside a microcontroller installed inside the board.We have used the open-source platform provided by the "Arduino IDE" to program the board and to receive the desired output.The board is programmed using C++ computer programming language.The program includes many of the internal Arduino Libraries which makes the program run better and makes it small in size consuming less memory.The Baud rate of the board is set to 9600 as default and the delay is given of 10000ms which means that the serial data transfer is to be done with a baud rate of 9600 between the Arduino board and computer while there will be a delay of 10000ms while recording the data.Coming up next is assigning a path for the data where it must be recorded on the SD card module.We need to have this data printed on our computer excel sheet or notepad wherever possible.For this very purpose, we recall the SD card module and gave it the recording properties.

Results & Discussion:
This data logger was kept active for 24 hours and readings were recorded.One of the 4 temperature sensor was embedded inside the soil to get Soil temperature, The 2 nd one was meant to check the atmospheric temperature, the 3 rd one was meant to keep inside the room which is to be ventilated and another one was to record the air inside the tube temperature.The readings that were recorded in SD card Module are as follows: The above data refers to the data recorded by Data logger at 10 second interval.Data recorded in temperature columns are in degree Celsius while time is in Hours-Minutes-Seconds.
We have achieved a temperature reduction of 10.4% in atmospheric air.

Conclusion
This paper helps us prove that geothermal HVAC system can be a sustainable and energy-efficient alternative to traditional heating, ventilation, and air conditioning systems.The experiment conducted on the set up gave us a temperature reduction of 10.4 %.By utilizing the constant temperature of the earth, geothermal systems can provide consistent heating and cooling while reducing energy consumption and operating costs.Although the initial installation costs of a geothermal HVAC system may be higher than traditional systems, the long-term savings in energy costs can make it a worthwhile investment.Additionally, geothermal systems have a longer lifespan and require less maintenance compared to traditional HVAC systems.Overall, geothermal HVAC systems offer a promising solution for reducing greenhouse gas emissions and increasing energy efficiency in the building sector.With advancements in technology and increased adoption, geothermal systems have the potential to play a significant role in reducing our carbon footprint and creating a more sustainable future.

9 NTU
represents the Number of Transfer Units, a dimensionless parameter that characterizes the heat transfer capability of the exchanger.UA is the overall heat transfer coefficient multiplied by the heat transfer area.It represents the overall heat transfer rate between the two fluids in the heat exchanger.
a) Wooden box b) Three types of Soils: Red Soil, Black Soil, and Laterite Soil.c) A data Logger with 4 temperature sensors d) 100W bulb e) Aluminum Foils

Figure 2 .
Figure 2. Wooden container box containing the soil and four Temperature sensors

Figure 3 .
Figure 3. Red soil with minimum Moisture Level Researcher's proposed CPCM-EAHE.This model (Cylindrical Phase Chane Material-Assisted Earth-Air Heat Exchanger) used a PCM (phase change material) to store heat and use it for further purposes.They derived calculations for analytical purposes of this process.
In this paper they have studied the model using a real life example to determine the use EAHE for a building.They have studied the single pipe design and multiple pipe design and determined the multiple pipe system is very effective.In this paper they have studied the flow of air in EAHE pipes and its changes between inlet and outlet air property.They have determined with experimental setup that the depth of 15 m gives the highest temperature drop 10Prospects of Shallow geothermal systems in HVAC for NZEB Irfan Ahmad Gondal 2020In this research paper they have together studied the concept of EAHE and NZEB (Net Zero Energy Building), they have also designed some ways of using GSHP, GHE and EAHE in enhancing the concept of NZEB building.In this paper the researcher have used the EAHE to get the heated air for winters and the were successfully in getting the temperature increase of 7.5 degree Celsius with pipe diameter of 2.85 cm and 2 m/s air velocity.

Table 2 .
Readings of Data Logger