Earth Tube Heat Exchanger Research Articles

A Review on Harnessing Nature's Heat with Earth Tube Heat Exchangers (ETHE)

This review paper presents a comprehensive review of recent advancements in Earth Tube Heat Exchanger. Through a meticulous examination of various scholarly papers, this review synthesizes and analyzes the significant contributions made by researchers in the field. Each paper reviewed offers unique insights and methodologies aimed at addressing key challenges and expanding the boundaries of knowledge in Earth Tube Heat Exchanger. This review provides a succinct summary of the methodologies employed, the findings obtained, and the implications of each study. The synthesis presented here underscores the diversity of approaches and the richness of ideas that characterize contemporary research in Earth Tube Heat Exchanger. From theoretical frameworks to empirical investigations, each paper contributes to a deeper understanding of the subject matter and suggests avenues for future exploration. By distilling the essence of each paper, this review serves as a valuable resource for scholars, practitioners, and students interested in gaining a nuanced understanding of the current state of research in Earth Tube Heat Exchanger. Furthermore, it highlights emerging trends, unresolved questions, and potential areas for further investigation, thereby fostering ongoing dialogue and innovation within the academic community. In conclusion, this review illuminates the collective efforts of researchers in advancing knowledge and addressing pressing issues within Earth Tube Heat Exchanger. It underscores the importance of interdisciplinary collaboration, critical inquiry, and methodological rigor in shaping the trajectory of future research endeavors.

A review on earth tube heat exchanger in heating and cooling systems

About 40% of the primary energy in the building sector is consumed for heating and cooling applications, where it started by relying on the use of sustainable energy sources through using an Earth tube heat exchanger (ETHE). ETHE is apparatus that works to transfer heat from ambient air to underground and vice versa which is used in heating and cooling applications. ETHE depends on undisturbed subsoil temperature, where the underground temperature doesn't change through the year at a certain depth. Ambient air passes through the buried heat exchanger in the ground and then cools down in summer and warms in winter. The good performance of this system depends on design efficiency. This paper reviews the experimental and numerical researches of ETHE which focuses on its design. The use of geothermal energy through ETHE leads to meeting energy demand and preserving the environment by reducing carbon dioxide emissions, which in turn affects the ozone.

Modeling of Combined Earth Tube Heat Exchanger and Solar Photovoltaic with Blower for Maintaining a Hospital Ward

Modeling of Combined Earth Tube Heat Exchanger and Solar Photovoltaic with Blower for Maintaining a Hospital Ward

Theoretical Analysis to Enhance the Effectiveness of Earth Tube Heat Exchanger

The temperature of atmosphere fluctuating continuously because the changing of environment, due to global warming effect that is uncomfortable for human beings. For comfort zone of human being air conditioning is use in summer season and heater is use in winter season. There for air conditioning and heater required high grade energy as well as high maintenance cost. Now replacing these devices by Earth tube heat exchanger. Earth tube heat exchanger is a device which is producing cooling effects in summer season and heating effects in winter season by passing the ambient air through the pipes inside the ground or soil as a source or sink of heat. According to previous research (IJERTCONV5IS02011) the effect of temperature at a certain depth about 2 m to 5 m remain nearly same throughout the whole year. The temperature inside the earth surface is greater than the atmospheric temperature in winter and less than the summer. Till date many researchers have done extensive research on Earth tube heat exchanger. The present study on this paper, focus on variation of temperature in buried pipes and enhance the various parameters of Earth tube heat exchanger that is reduced the cost and energy consumption for same desired effect. And also replace the other pipe with PVC pipe at 1524mm (6 inches) internal diameter as a varying length and 250-watt blower is use to flow the air at 2-5 m/s.

Earth Tube Heat Exchanger

Abstract: Devices that utilise the ground as a wellspring of or sink for warming or cooling are called ground-to-air heat exchangers, ground pipe heat exchangers, or soil heat exchangers. Numerous concepts and experiments with EAHE have so far been developed and tested to determine the best parameter values to increase performance based on location and other variables. In this study, we will review the studies conducted so far from the viewpoint of performance evaluation considering the influence of various parameters such as construction materials, depth from the ground surface, wind speed, and pipe length.

A Review Paper on Computational Study of Earth Tube Heat Exchanger System

Abstract: Earth Tube heat exchanger can be proved as a better substitution to the space heating and HVAC problems that we face in our day to day lives. Earth tube heat exchangers can work in two phases, i.e. as a heater during winter seasons and as a cooler during summer season. ETHE can work more efficiently than traditional HVAC. This project concentrates on computational study of earth tube heat exchanger. The designing calculations were done for appropriate length and area of an earth tube heat exchanger. A model of ETHE was produced on basis of this calculations and dimensions obtained. The model was generated using Solidworks R2021 software. The ETHE model generated was then analysed for thermal stresses, distribution and other parameters. A CFD simulation of model for velocity and flow was carried on. The conclusions obtained show that ETHE works efficiently and can be used as a substitution for traditional HVAC. Keywords: Heating ventilation and air conditioning(HVAC), Earth tube heat exchanger(ETHE), Computational fluid Dynamics (CFD), Efficiently, Thermal stresses.

Reducing The Thermal Deviation Inside Greenhouses by Using Solar Heating and Earth Tube Heat Exchanger Systems

Reducing The Thermal Deviation Inside Greenhouses by Using Solar Heating and Earth Tube Heat Exchanger Systems

Heat Pump Design for Simultaneous Cooling Space and Heating Water Coupled with Earth-Tube Heat Exchanger as Secondary Heat Sink

A heat pump for simultaneous heating and cooling (HPS) is more efficient in energy and beneficial
 in use than a reversible heat pump which works in either direction to provide heating or cooling. A HPS is usually coupled with a thermal storage tank for possibly operating in 3 modes: heating mode, cooling mode, and simultaneous heating and cooling mode. To improve the HPS performance in heating mode or cooling mode, the HPS should be installed an auxiliary equipment in order to reject overheat in the system or to absorb supplemental heat into the system. This paper proposed a design of a HPS for cooling space and hot water production coupled with a horizontally shallow earth-tube heat exchanger as secondary heat sink for Thai residences in which the main components in the design are composed of the condenser and the earth tube heat exchanger. The coefficients of performance (COP) of the HPS were evaluated by the experiments. The results showed that it could work the best performance when it worked in simultaneous cooling and heating mode at the water flow rate of 6.0 L/min with the coefficient of performance (COP) of 6.3±3.1 %. The HPS had high efficiency and it worked continuously in cooling mode when it operated in the nighttime with the average COP of 4.3±14.5 %. However, an efficiency of the HPS was declined when heat gain in the conditioned room is significantly increased by high intensity of solar radiation in the daytime with the average COP of 2.5±14.5 %.
 HIGHLIGHTS
 
 Energy used for cooling or heating systems such as air-conditioning and hot water production is predominantly effect to total energy use in residential sector in many countries including Thailand
 A heat pump for simultaneous heating and cooling (HPS) for cooling space and hot water production coupled with thermal storage tank and a horizontally shallow earth-tube heat exchanger as secondary heat sink were designed for Thai residences
 This HPS could work the best performance when it worked in simultaneous cooling and heating mode
 For only cooling mode, this HPS worked continuously with high performance when it operated in the nighttime but in the daytime it still worked continuously with lower performance
 
 GRAPHICAL ABSTRACT

Potential reduction in water consumption of greenhouse evaporative coolers in arid areas via earth-tube heat exchangers

This study aimed to explore the potential of developing a novel cooling system combining a greenhouse and an earth-tube heat exchanger (ETHE). In this system, greenhouse air is circulated through the underneath soil mass to use the deep-soil cooling effect. This was achieved through the following steps. First, soil temperature profile inside and outside the cultivated greenhouse was monitored for almost one year to study the possibility of using deep-soil coldness for cooling the greenhouse air. Second, a prototype ETHE was built to practically investigate the potential reduction in air temperature as the air flows inside the deep earth pipes. Third, a prototype greenhouse was erected to study the ETHE concept. Results from the first experiment revealed that soil temperature at a soil depth of 2.5 m inside the greenhouse offers good conditions to bury the ETHE. The soil temperature at this soil depth was below the maximum temperature (32°C) that most greenhouse crops can withstand. Results from the prototype ETHE showed a slight reduction in air temperature as it passed through the pipes. From the prototype of the integrated greenhouse and ETHE system, reduction in air temperature was observed as the air passed through the ETHE pipes. At night, the air was heated up across the ETHE pipes, indicating that the ETHE was working as a heater. We concluded from this study that greenhouses in arid climates can be cooled using the ETHE concept which would save a large amount of water that would otherwise be consumed in the evaporative coolers. Further investigations are highly encouraged.

Earth tube heat exchanger design for efficiency enhancement of PV panel

PV panel or Photovoltaic panels are semi-conducting materials to convert solar energy into electrical energy. According to the Standard Test Conditions, the best operating condition of the PV panel is at 25 °C. For countries like Saudi Arabia, Libya, Yemen and much other have atmospheric temperature of about 40 °C. At this temperature, the performance of the PV panel degrades. In this current paper a heat exchanger is designed numerically in exact dimensions to carry out thermal cooling of the PV panels, with motive to improve the performance of PV panels even at elevated temperatures. Aluminium pipe of 50 m long, 10 cm internal diameter with 40 fins/m length is selected for designing. This increases the efficiency of the panel and the convective heat transfer rate with lower pressure drop.

CFD Analysis of Geothermal Heat Exchanger at Different Orientation

The main objective of present work to investigate the arrangements of piping system of earth tube heat exchanger for better thermal comfort. For these work CFD analysis on three different designs of earth tube heat exchanger for summer and winter session for Bhopal location have been performed. computational fluid dynamics analysis have been performed on earth tube heat exchanger using horizontal pipe at various air velocity such as 0.5m/sec, 1 m/sec, 2m/sec, 3m/sec, 4m/sec & 5m/sec for summer session, to get temperature distribution inside the earth tube heat exchanger. Results show that there are drop of temperature in summer session range from 318K to 296K and rise of temperature in winter session range from 288K to 296.7K. It has been observed from the results of computational fluid dynamic analysis that the earth tube heat exchanger using horizontal pipe gives better result as compared with vertical and inclined piping arrangement. So it is recommended that the earth tube heat exchanger using horizontal pipe arrangement may be used for better thermal comfort.

THE THERMAL POTENTIAL OF AN EARTH TUBE HEAT EXCHANGER SYSTEM IN AIR TEMPERATURE MODERATING

The potential of earth tube heat exchangers in tempering ventilation air in delta region was studied experimentally by using two diffident systems. The two systems were installed at the research farm, faculty of agriculture, Kafrelsheikh University (31.07° N and 30.57° E), Kafrelsheikh governorate, Egypt. The first system (S1) consisted of one pipe with inner diameter of 10.85 cm. The second system (S2) consisted of two coaxial pipes the first pipe with inner diameter of 10.85 cm surrounded by the other one with inner diameter of 16.2 cm and the annular space between them filled by water and sealed. The length of both systems was 12 m and buried at a depth of 75 cm within two ditches 5 m apart and refilled with earth. The ambient air was blown by a 0.75 kW blower to pass through the two buried systems. The systems were operated during cooling and heating modes at four operating durations and five air velocities. It was found that, the maximum temperature reduction and rise were 12.65 °C at air velocity 1.8 m/s, 12 hours operating duration and 6.27 °C at velocity 3.7 m/s, 12 hours operating duration under cooling and heating modes for S1 respectively. Maximum thermal energy rate removed during cooling mode was 679.9 W for S2 at air velocity 9.7 m/s and 22 hours operating duration and the corresponding COP was 3.96. The maximum thermal energy rate added during heating mode was 629.7 W for S1 at air velocity 9.7 m/s, 12 hours operating duration and the corresponding COP was 3.67. Both systems contribute in air temperature control which declares in diminishing its amplitude. It was found that when the air velocity (mass flow rate) increase the thermal energy rate removed / added increases although the temperature reduction / rise decreases. This was because of the effect of increasing mass flow rate was predominant than the effect of temperature reduction/ rise in thermal energy rate exchanged evaluation. Key words: Earth tube, thermal potential, earth to air heat exchanger

Assessment of Environment Control in Arid Area Green house coupled with Earth Tube Heat Exchanger

In hot arid regions, yields are low and unstable, growing season limited to one. Greenhouses can stabilize and improve yields and extend seasons. But their adoption is impeded by the requirement of large amount of water for (evaporative) cooling. Arid Area Greenhouse (AAG) is developed to reduce or eliminate this need by employing earth-tube-heat-exchanger (ETHE). ETHE was able to heat the greenhouse from 9°C to 22-23°C in 30 minutes in the cold winter nights. Static ventilation along with shading was effective for day time to control till early March. Subsequently ETHE was also operated. Yield of tomato in Arid Area Greenhouse was 1.5 to 2 times and water saving in AAG was 44% of that in open-field condition. ETHE and natural ventilation hold promise as environmental control devices for greenhouses in hot arid regions.

Review of Earth Tube Heat Exchanger

Review of Earth Tube Heat Exchanger

STUDYING SOME OF THE EARTH TUBE HEAT EXCHANGER AND SOILS PROPERTIES

In this paper the composition and thermal property of soil and pipe of earth tube heat exchanger are discussed. The main factors that impact the soil thermal properties and several commonly-used pipe materials are studied. The impact of soil thermal conductivity and pipe thermal conductivity on the soil temperature field around the buried pipe is very important. As an energy-saving and environment friendly air conditioning technology, earth tube heat exchanger has been utilized wildly for some years. It is necessary to study in detail soil properties and pipe materials for utilizing earth tube heat exchanger successfully. The thermal conductivity for sandy soil is higher than sandy clay loam soil and heat exchange rate between air in metal pipe and soil achieve more 5 time for PVC pipe and wet soil with 15% moisture achieve heat exchange rate to air in pipe by 5% more dry soil.

GREENHOUSE COOLING USING EARTH-TUBE HEAT EXCHANGER AND EVAPORATIVE COOLING FOR DURING SUMMER SEASON

In this research work an attempt has been made to analysis the thermal performance of the earth-tube heat exchanger (ETHE) during summer season of 2012 (June to September). The experimental work was executed in the experimental farm of Faculty of Agriculture, Suez Canal University, Ismailia Governorate, Egypt (Latitude angle of 30.62oN, Longitude angle of 32.27oE, and mean altitude above sea level of 5 m). The ETHE technique was used to utilize the stability of deep soil temperature for reducing the indoor air temperature during the summer season. A computer simulation model has been developed and used based on MATLAB program to determine the depth at which the soil temperature is stabilized. A comparative study between the evaporative cooling system (based on fan-pads system) and the ETHE system was carried out during the summer season to compare weather the two cooling systems differed significantly in the cooling effectiveness to provide and maintain the indoor air temperature within the two greenhouses at the desired level. The obtained data showed that, the depth at which the soil temperature is stabilized was achieved at 3 m deep. The overall thermal efficiency of the ETHE system was 73.85 %. Due to the microclimatic conditions (air temperature and air relative humidity) were at and around the desired level, the growth rate, flowering rate, fruit set rate, and fresh yield of cucumber crop were at high rates and good quality. Data of the computer simulation model of the indoor air and soil temperatures were found to be very closest to that measured.

THERMAL PERFORMANCE FOR GREENHOUSE HEATING BY USING EARTH-TUBE HEAT EXCHANGER DURING WINTER SEASON

In this research work an attempt has been made to analysis the thermal performance of the earth-tube heat exchanger (ETHE) during winter season of 2012-2013 (December to March). The experimental work was executed in the experimental farm of Faculty of Agriculture, Suez Canal University, Ismailia Governorate, Egypt (Latitude angle of 30.62oN, Longitude angle of 32.27oE, and mean altitude above sea level of 5 m). The ETHE technique was used to utilize the stability of deep soil temperature for worming the indoor air of greenhouse cucumber during winter season, and reducing the indoor air temperature during the summer season. A computer simulation model has been developed and used based on MATLAB program to determine the depth at which the soil temperature is stabilized. The obtained data showed that, the depth at which the soil temperature is stabilized was achieved at 3 m deep. The overall thermal efficiency of the ETHE system during winter season (heating process) was 72.90 %. Due to the microclimatic conditions (air temperature and air relative humidity) were at and around the desired level, the growth rate, flowering rate, fruit set rate, and fresh yield of cucumber crop were at high rates and good quality. Data of the computer simulation model of the indoor air and soil temperatures were found to be very closest to that measured.

A Proposed ‘Water Tube Heat Exchanger’ Space Cooling System Performance Analysis

Increasing energy demand for domestic space cooling in Kerala, India, necessitates innovations in the passive systems. Earth tube heat exchangers (ETHE) are gaining popularity in the architectural practice of the region. Owing to the higher specific heat of water and the other underlying principles of the ETHE, there is a possibility of developing a similar system by replacing earth with water as the heat exchange medium. A conceptual water tube heat exchanger (WTHE) system was designed, which consists of a 45 m long PVC pipe staggered in an underground reinforced concrete rain water harvesting tank connected to a house. Performance of the system was assessed using the 'Psychrometric Chart+Duct Calculator V4.3 simulation tool. Later, this system was developed on site and its performance was analysed. The simulation predicted a maximum difference of 4.7°C between the inlet and outlet air temperatures. However, a difference of 8.4°C was achieved by the proposed WTHE system built.

Thermal modeling aspects of solar greenhouse microclimate control: A review on heating technologies

Modeling of greenhouse microclimate is very important to maintain optimum inside environment during different stages of plant growth. To formulate an accurate thermal model, computation of precise solar radiation input and overall heat transfer coefficient is important as these affect the greenhouse energy and mass balance. Initially, we briefly review the modular studies related to solar radiation capture and overall heat transfer coefficient for greenhouse applications. Numerous thermal models have been developed to describe the microclimate of a greenhouse and validated at various locations, climates and crops. We review all these independent thermal models (static as well as dynamic) and discuss in detail the representative ones. In adverse winter climatic conditions, greenhouse has to be coupled with various active or passive heating systems to maintain the inside microclimate according to crop needs. We also review greenhouse thermal models integrated with heating/heat storage systems such as: rock-bed, phase change materials, earth-tube heat exchanger systems, all types of water heating systems (water thermal mass storage, heat-pipe heating system, shallow solar pond heating systems, geothermal based heating systems viz. ground source heat pump system, solar-assisted ground source heat pump system, aquifer coupled heat exchanger system), ground air collector system, north wall and thermal curtain, and soil heat exchanger system. Important aspects of each representative model such as: type, tool/program used for solution/simulation, input data used to run simulations, interactive components, parameters studied, assumption made, important model characteristics and results obtained are discussed at length. Based on the compiled information, a generalized procedure is devised to formulate greenhouse thermal model. Finally, based on the main characteristics and results of the study, some important conclusions are drawn and suggestions made for further studies.

Effectiveness of the earth tube heat exchanger system coupled to a space model in achieving thermal comfort in rural areas

The aim of this work is to investigate by modelling the possibility of reducing the operational energy of a typical house without negatively affecting its embodied energy. This is done through consideration of different building materials coupled with the use of an earth to air heat exchanger (EAHE) for fresh air supply and cooling. For known indoor and outdoor conditions and for given building materials (thermal capacity and conductance), a ventilation controller determines the amount of flow rate needed to temperate the indoor air temperature to achieve thermal comfort. Different wall configurations are assumed for each of the living zone and the bedroom zone of the apartment. It is found that the use of an optimal wall configuration in each zone coupled with the EAHE results in 76.7% energy savings compared with the reference case with conventional cooling.