Numerical Research and Parametric Study on the Thermal Performance of a Vertical Earth-to-Air Heat Exchanger System

The earth-to-air heat exchanger (EAHE) system, as a clean and efficient shallow geothermal energy application technology, has obvious effects in reducing the energy consumption of passive low-energy buildings. The traditional horizontal EAHE system is difficult to apply and popularize due to its large occupation, unfavorable shallow soil temperature, and difficulty in timely centralized discharge of condensed water. This paper proposes a new type of vertical earth-to-air heat exchanger (VEAHE) system. The VEAHE system has a number of advantages such as smaller occupation, efficient geothermal energy utilization, and centralized discharge of condensed water. In order to evaluate the influence of different parameters on the thermal performance of the VEAHE system, a mathematical model of the VEAHE system was developed. And, the data calculated by the model highly tallied with the experimental data. The results showed that laying thermal insulation layers at the outlet of risers will effectively restrain the interference of downcomers to risers. It is advisable to set thickness and length of the insulation layer at 30 mm and 3 m. Considering the compromise between thermal performance and construction costs of the VEAHE system, the length of the ducts at 30–50 m and the diameter at 150–250 mm are recommended. The air supply volume of a single shaft can reach 500–1200 m3/h as the air velocity reaches 3–7 m/s.

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Parametric Optimization of Earth to Air Heat Exchanger Using Response Surface Method

Sustainability ◽

10.3390/su11113186 ◽

2019 ◽

Vol 11 (11) ◽

pp. 3186 ◽

Cited By ~ 2

Author(s):

Maoz Maoz ◽

Saddam Ali ◽

Noor Muhammad ◽

Ahmad Amin ◽

Mohammad Sohaib ◽

...

Keyword(s):

Heat Exchanger ◽

Response Surface ◽

Response Surface Method ◽

Geothermal Energy ◽

Energy Utilization ◽

Soil Conditions ◽

Cooling Load ◽

Air Velocity ◽

Pipe Length ◽

Surface Method

The achievement of sustainable energy goals warrants keen interest in promoting efficient buildings and renewable energy resources. Prominent among the energy-efficient building technologies is geothermal energy, which has a significant margin for improving energy utilization related to Heat, Ventilation, and Air Conditioning (HVAC). However, the efficient extraction of geothermal energy for HVAC applications requires stringent control of geometric parameters, boundary conditions, and environmental conditions. In this study a new approach has been devised to optimize the open loop Earth to Air Heat Exchanger (EAHE) system using a statistical optimization technique i.e., Response Surface Method (RSM). The study was conducted in the soil and weather conditions of Peshawar city in Pakistan. Parametric analysis was conducted for the three influencing variables, i.e., the pipe length, diameter, and air velocity using the EAHE model. The soil model predicts temperature in the range 20–26 °C for Peshawar at a depth above 3 m. Response Surface method was used to optimize the pipe length, diameter, and air velocity of the EAHE system. Analysis of Variance (ANOVA) indicates that all the three factors are significant. The EAHE system can effectively reduce the temperature by 15–18 °C and compensate the cooling load of single room for the parameters in the ranges of 50–70 m for the length, 0.18–0.25 m for the diameter, and 5–7 ms−1 for the air velocity. A regression equation is developed to predict the cooling load for any input values of the three influencing variables according to the weather and soil conditions.

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Thermal performance of a residential house equipped with a combined system: A direct solar floor and an earth–air heat exchanger

Sustainable Cities and Society ◽

10.1016/j.scs.2018.05.012 ◽

2018 ◽

Vol 40 ◽

pp. 534-545 ◽

Cited By ~ 6

Author(s):

Mohammed Cherif Lekhal ◽

Rafik Belarbi ◽

Abderahmane Mejedoub Mokhtari ◽

Mohammed-Hichem Benzaama ◽

Rachid Bennacer

Keyword(s):

Heat Exchanger ◽

Thermal Performance ◽

Combined System ◽

System A ◽

Residential House

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Polymeric Hollow Fiber Heat Exchangers (PHFHEs): A New Type of Compact Heat Exchanger for Lower Temperature Applications

Heat Transfer: Volume 4 ◽

10.1115/ht2005-72590 ◽

2005 ◽

Cited By ~ 3

Author(s):

Dimitrios M. Zarkadas ◽

Baoan Li ◽

Kamalesh K. Sirkar

Keyword(s):

Heat Transfer ◽

Heat Exchanger ◽

Thermal Performance ◽

Hollow Fiber ◽

Heat Exchangers ◽

Operating Cost ◽

Polymer Materials ◽

Steam Condensation ◽

New Type ◽

Shell And Tube

Plastic heat exchangers are characterized by an inferior thermal performance compared to their metal counterparts. Therefore, their usage is mainly limited to handling corrosive media or when ultra high purity is required, e.g., pharmaceutical industry. Polymeric Hollow Fiber Heat Exchangers (PHFHEs) have recently been proposed [1] as a new type of heat exchanger that can overcome these constraints and offer the same or better thermal performance than metallic shell and tube or plate heat exchangers while occupying a much smaller volume. In this paper we report our results for heat transfer in PHFHEs with both parallel and cross flow in the shell side of the device. Fibers made of polypropylene (PP) and polyetheretherketone (PEEK) were tested. In addition, steam condensation studies in PHFHEs are reported for the first time. The overall heat transfer coefficients achieved for water-water and water-brine systems are as high as 1400 Wm−2K−1. These values are higher than any value reported for plastic heat exchangers and comparable with commonly acceptable design values for metal shell and tube heat exchangers. Similar coefficients were obtained for steam condensation. Polymeric hollow fiber heat exchangers can also achieve high thermal effectiveness, large number of transfer units (NTU) and very small height of a transfer unit (HTU), if properly rated. If designed like commercial membrane contactors, they can achieve up to 12 transfer units in a single device, not longer than 60–70 cm! In addition, the conductance per unit volume PHFHEs achieved was up to one order of magnitude higher compared to metal heat transfer equipment. This superior thermal performance is also accompanied by considerably lower pressure drops. Therefore, the operation of PHFHEs will be characterized by a low operating cost. Combined with the much lower cost, lower weight and elimination of metal contamination polymer materials offer, it is obvious that PHFHEs constitute a potential substitute for metal heat exchangers on both thermal performance and economical grounds. Possible application fields include the food, pharmaceutical and biomedical industries as well as applications where corrosion resistant, light and very efficient devices are required, i.e., desalination, solar and offshore heat transfer applications.

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Numerical model for geothermal energy utilization from double pipe heat exchanger in abandoned oil wells

ADVANCES IN GEO-ENERGY RESEARCH ◽

10.46690/ager.2021.02.10 ◽

2021 ◽

Vol 5 (2) ◽

pp. 212-221

Author(s):

Zhongyue Lin ◽

Kang Liu ◽

Jing Liu ◽

Dandan Geng ◽

Kai Ren ◽

...

Keyword(s):

Heat Exchanger ◽

Numerical Model ◽

Geothermal Energy ◽

Oil Wells ◽

Energy Utilization ◽

Double Pipe ◽

Pipe Heat

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Effects of Supply Parameters of Stratum Ventilation on Energy Utilization Efficiency and Indoor Thermal Comfort: A Computational Approach

Mathematical Problems in Engineering ◽

10.1155/2021/6615148 ◽

2021 ◽

Vol 2021 ◽

pp. 1-16

Author(s):

Lina Zhang ◽

Yanhui Mao ◽

Qiu Tu ◽

Xiaogang Wu ◽

Lingyu Tan

Keyword(s):

Thermal Comfort ◽

Thermal Performance ◽

Energy Utilization ◽

Utilization Efficiency ◽

Airflow Rate ◽

Heating Condition ◽

Indoor Thermal Comfort ◽

Supply Angle ◽

Air Supply ◽

Ventilation Effectiveness

Stratum ventilation shows the significant potential on energy conservation and indoor thermal comfort under cooling applications. Yet, only limited researches focus on the thermal performance of stratum ventilation under heating condition. The heating and cooling operation characteristic of stratum ventilation is different due to the distinct airflow characteristics. Therefore, this paper investigated the parameters that affect energy utilization efficiency and indoor thermal comfort under heating condition served by stratum ventilation via CFD simulations approach. The supply air parameters included temperature, airflow rate, angle, and return air outlet positions. The evaluation indicators adopt ventilation effectiveness and effective draft temperature (EDT) for assessing the energy utilization efficiency and indoor thermal comfort served by stratum ventilation under heating condition. The results demonstrated that, under the heating mode of stratum ventilation, different effects on the thermal performance were made by the mentioned parameters. The ventilation effectiveness was higher when the air supply temperature is 26°C, airflow rate is 7 air change per hour (ACH), and the air supply angle is 45°. The EDT range of the occupied zone is closest to zero K when the air supply temperature is 28°C, airflow rate is 12 (ACH), and the air supply angle is 60°. The related conclusions obtained from this study provide the theoretical basis for the stratum ventilation design and promote its heating application.

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Concepts and characteristics of a U-shaped docking well geothermal heat extraction system

Energy Exploration & Exploitation ◽

10.1177/0144598719832712 ◽

2019 ◽

Vol 37 (2) ◽

pp. 865-883 ◽

Cited By ~ 1

Author(s):

Li Li ◽

Xiantao Liu ◽

Dong Xiao ◽

Kun Huang ◽

Shuxuan Li

Keyword(s):

Heat Transfer ◽

Geothermal Energy ◽

Transfer Effect ◽

Energy Utilization ◽

Heat Extraction ◽

Extraction System ◽

Geothermal Heat ◽

New Type ◽

Deep Geothermal Energy ◽

Effective Use

Environmental pollution in China is getting worse. The effective use of geothermal energy can solve the problem of greenhouse gas emissions. This paper introduces a new type of medium-deep geothermal energy utilization system named U-shaped docking well geothermal heat extraction system and analyzes its characteristics. The results show that the system can meet the needs of daily heating, and the heat transfer effect of this system is greater than the concentric casing heat exchange systems. This study provides a new idea for the use of medium-deep geothermal energy.

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