Performance Of Earth-air Heat Exchanger Research Articles

An earth-air heat exchanger integrated with a greenhouse in cold-winter and hot-summer regions of northern China: Modeling and experimental analysis

This study aimed to investigate the thermal performance of Earth-Air Heat Exchangers (EAHE) in greenhouses in northern China's cold winter and hot summer regions. The experiment was conducted in two identical greenhouses (with and without an EAHE), and a mathematical and Computational Fluid Dynamics (CFD) simulation model was established to predict the air temperature inside the greenhouse and heat exchanger outlets and verified with measured data. Parametric analysis was also performed, and the effect of long-period application was evaluated. The results showed that the data calculated by the model agreed well with the experimental data. The average differences between the inlet and outlet air temperatures of the EAHE, daily average heat exchange capacity, and coefficient of performance (COP) was 9.26 ℃, 18.86 MJ, and 22.49 in winter, respectively, while in summer, they were 10.55 ℃, 18.78 MJ, and 23.52, respectively. The night-time temperature of the greenhouse increased by 1.43 °C during winter, while the temperature during summer daytime was reduced by 2.10 ℃. An increase in the pipe length improves the heat exchange efficiency, the heat exchange mainly occurs in the first half of the horizontal pipe, and the increase in air velocity and operation time will reduce the heat exchange efficiency. In conclusion, the system was proposed as a viable auxiliary device for greenhouse heating and cooling in cold winter and hot summer regions and to reduce greenhouse gas emissions. The system is recommended to be arranged outdoors for cooling and indoors for heating.

Performance of earth-air heat exchanger in cooling, heating, and reducing carbon emissions of an industrial poultry farm: A case study

ABSTRACT This paper aims to study an earth-air heat exchanger system proposed to cover the living environment needs and reduce energy consumption and greenhouse gas emissions of an industrial poultry house in southern Algeria. For this purpose, a detailed mathematical model was used to determine the thermal needs of this industrial building. The soil temperature was studied to estimate the appropriate depth for installing the earth-air heat exchanger, followed by a parametric and economic study to determine its dimensions and cost. Finally, compare its performance with the systems currently used in this industrial farm. The study results, which were obtained in extreme working conditions, showed that the earth air heat exchanger could cover 45% and 38% of the heating and cooling demands, respectively. In summer, the proposed heat exchanger was able to reduce the temperature from 47°C to 27.1°C, while in winter, it was able to increase the temperature from 4.8°C to 22.9°C, and its performance was stable compared to the systems currently used, and, it recorded temperatures better under hot outside conditions. Furthermore, its use reduces CO2 emissions to 719 kgCO2/day in heating and 2531 kgCO2/day in cooling, making it a suitable solution for this type of industrial building.

Characterizing soil’s thermal property for earth air heat exchanger through experiment

The energy holding or dissipating capacity of soil is an important parameter for an earth air heat exchanger (EAHE). The present work deals with the experimental investigation of the thermal character of four distinct soil samples to assess the EAHE performance. The EAHE has been modelled as a heat source and the responses of soil samples as a function of time were recorded through a data logger. Results reveal that a soil sample has more effective thermal character compared to other samples for better performance of EAHE. For 6 h of continuous operation, the soil temperature was found to rise by 8 °C, which is the least among all the remaining samples. It is concluded that for longer continuous operation of EAHE, the soil with less thermal storage capacity, which has the potential to dissipate heat quickly, is better. The present study would be useful for EAHE designers to select an appropriate site.

Effect of geo-climatic conditions and pipe material on heating performance of earth-air heat exchangers

Climatological and geological site classification intended for Earth-Air Heat Exchanger Technology (EAHE) is an important factor in the design, implementation and optimal operation of such system. In this context, this paper presents an investigation on the heating performance and operating feasibility of two EAHEs in three different geo-climatic regions in Algeria. First, the performances of the EAHEs were experimentally studied in the temperate Oran climate and the corresponding results were used for validation of the numerical part. The experiment allowed to analyze the effect of the pipe material on the performance of the two EAHEs that are made of different materials (PVC and Zinc). After validation of the numerical part, the study was extended to three different climates including a temperate climate for Oran, an arid climate for Bechar and a steppe climate for El-Bayadh cities. For these climates, the heating study is rarely considered in this context. Furthermore, a sensitivity analysis was conducted in order to evaluate the operating feasibility of the EAHEs in the considered regions. The results revealed that the Zinc EAHE is more efficient in a temperate climate with a COP of 9.5 than in an arid or steppe climate with a COP of 8.2 or 8.1, respectively. However, the PVC EAHE is much better in an arid climate with a COP of 9.4 than in a temperate or steppe climate with a COP of 7.6 or 8.4, respectively. Otherwise, both EAHEs exhibited similar behavior in a steppe climate. The results show that the thermal performance of EAHE mainly depends on geo-climatic conditions and the type of pipe material.

Thermal and infrared camouflage performance of earth-air heat exchanger for cooling an underground diesel generator room for protective engineering

Research on earth-air heat exchanger (EAHE) systems focuses on their energy efficiency for civil and industrial buildings. For cooling the protective engineering’s diesel generator room, outlet temperature of EAHE system should be controlled within a certain range close to the outdoor temperature to avoid infrared exposure to military reconnaissance. This study proposed a cooling method for the protective engineering’s diesel generator room by using the engineering’s tunnel as a EAHE. At the beginning, recommended velocity was proposed to meet the infrared camouflage requirement. In addition, influencing parameters including the heat generated in the diesel generator room, soil temperature, and average value and magnitude of outdoor temperature are studied. Also, 3 intermittent modes are simulated. For all simulations, both the cooling capacity and the infrared-camouflage-guaranteed duration are compared. Results show that this system is suitable for small-scale engineering with high average outdoor temperatures and low temperature difference between day and night. The intermittent ventilation significantly improved the infrared camouflage effect while it works but not the total cooling capacity because of the shorter working hours. The infrared-camouflage-protection duration increased by 29.96% as the system intermitted every 9 h, compared with that under non-intermittent ventilation condition.

Working parameters affecting earth-air heat exchanger (EAHE) system performance for passive cooling: A review

The study on the effect of the working parameters such as pipe material, pipe length, pipe diameter, depth of burial of the pipe, air flow rate and different types of soils on the thermal performance of earth-air heat exchanger (EAHE) systems is very crucial to ensure that thermal comfort can be achieved. In the past decade, researchers have performed studies to develop numerical models for analysis of EAHE systems. Until recently, two-dimensional models replaced the numerical models in the 1990s and in recent times, more advanced analysis using three-dimensional models, specifically the Computational Fluid Dynamics (CFD) simulation in the analysis of EAHE system. This paper reviews previous models used to analyse the EAHE system and working parameters that affects the earth-air heat exchanger (EAHE) thermal performance as of February 2017. Recent findings on the parameters affecting EAHE performance are also presented and discussed. As a conclusion, with the advent of CFD methods, investigational work have geared up to modelling and simulation work as it saves time and cost. Comprehension of the EAHE working parameters and its effect on system performance is largely established. However, the study on type of soil and its characteristics on the performance of EAHEs systems are surprisingly barren. Therefore, future studies should focus on the effect of soil characteristics such as moisture content, density of soil, and type of soil on the thermal performance of EAHEs system.

On the Design of Two EAHE Assemblies with Four Ducts

This article applies the constructal design method to analyze how to improve the thermal performance of earth-air heat exchangers (EAHE) composed by four ducts. The paper evaluates two types of arrangements for which the centers of the ducts take the shape of rectangles and diamonds. Under volumetric constraints, the vertical Sv and horizontal Sh spacings between the ducts are left free to vary. The objective is to maximize the magnitude of the EAHE instantaneous thermal potential P which is an average of the differences between the temperatures at the ducts outlets and inlets at any instant of time. The temperature fields are computed through numerical simulations, adopting a verified and validated three-dimensional model. Among the results, this work shows how the design can raise by 11% the annual thermal efficiency of the EAHE.

Transient Models to Analyze the Influence of the Air Velocity and Ducts Diameter on the Performance of Earth-Air Heat Exchangers

Transient Models to Analyze the Influence of the Air Velocity and Ducts Diameter on the Performance of Earth-Air Heat Exchangers