Earth Air Tunnels

 Earth Air Tunnels.

Earth - air heat exchanger (EAHE) is a promising method that can be used effectively to reduce the heat / cooling load of a building by heating the air in winter and vice versa in summer. Over the past two decades, a number of studies have been conducted to improve the analysis methods and numerical analysis methods of EAHE programs. Many researchers have developed sophisticated calculations and processes but cannot be easily manipulated in design scales and should be used in a flawed and error-free manner. In this paper, the author has developed a three-dimensional model of EAHE systems using a set of simplified estimates. The uninterrupted earth temperature (EUT) calculation method and the newly developed factor factor factor and Nusselt number are used to ensure maximum accuracy in calculating heat transfer. Improved equations enable designers to calculate heat transfer, coefficient of relative heat transfer, pressure reduction, and pipeline length of the EAHE system. A long pipe with a small diameter buried at great depth and having a low air velocity leads to an increase in the efficiency of the EAHE system.

Over the past two decades, much research has been done to improve the analysis methods and numerical analysis methods of EAHE systems (Mihalakakou et al. 1994; Bojic et al. 1997; Gauthier et al. 1997; Hollmuller and Lachal 2001; Su et al. 2012; Sehli et al. 2012 ; Ozgener et al. 2013). EAHE performance analysis includes calculations of heat transfer transfer from pipe to ground or calculation of heat transfer from circulating air to pipe and changes in air temperature and humidity. Many computer modeling tools are available commercially. EnergyPlus and TRNSYS have well-functioning EAHE modules; however, these are analytical tools and were not immediately used in construction.

Currently, Computational Fluid Dynamics (CFD) is very popular among model investigators and performance evaluators of EAHE programs. CFD uses a simple rule to separate the entire system into smaller grids. Control figures were then used in these subdivisions to obtain numerical solutions for flow limits, pressure distribution, and temperature gradients in the shortest time and at the appropriate cost due to the reduction of the required test activity (Kanaris et al. 2006; Wang et al. 2007). A thorough analysis of the EAHE system, recommends the use of CFD, but is limited to those with a good command over it. With the initial introduction of the EAHE system, the use of basic heat transfer measurements is appropriate to determine the size of the geometric system. Many researchers such as De Paepe and Janssens (2003), Badescu and Isvoranu (2011), and T'Joen et al. (2012) developed EAHE estimates and procedures.

In this paper, the author has developed a single complex model of the EAHE system. The EUT calculation method and the recently developed correlation of the factor factor and the Nusselt number are used to ensure maximum accuracy in calculating heat transfer.

EAHE analysis and modeling

The development of the EAHE system model involves the use of basic heat transfer calculators. The geometric dimensions of the EAHE system are determined by taking into account the amount of heat or cooling load that must be met by building the building space. The design process includes identifying user-defined input parameters and parameters that affect the output of the desired design. Once the design output is ready, the heat transfer equations are used to meet the desired product in terms of installation.

Therefore, depending on the nature of the problem of designing the air flow rate, ṁ; air temperature, T in; desirable air temperature from EAHE, T out; and EUT is considered a parameter of the measurement problem. In addition, it is assumed that the installation location of the EAHE system is known. Therefore, the ambient air temperature and soil properties are known. The EUT temperature is estimated to be the average annual air temperature in a particular area; therefore, it is also considered a known parameter. Air flow rate and air temperature set are set by design requirements.

The geometric sizing parameters of EAHE include pipe diameter, D; pipe length, L; and the number of pipes respectively, N p, at the terminal.


The following assumptions are made to facilitate the development of a single type of EAHE system rating:

Global warming is defined as the equivalent of the same air temperature, equal to the incoming air temperature.

The EUT can be measured at a moderate local temperature (Bhopal, India).

The polyvinyl chloride (PVC) pipe used in EAHE is under the same category.

The size of the pipeline used in EAHE is very small; therefore, the thermal resistance of the pipe material is minimal.

The temperature on the surface of the pipe is similar to the axial direction.