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One of the highly efficient sources of renewable energy is the Ground Source Heat Exchangers (GSHE). Thermal interaction effects between boreholes cause a decrease in the efficiency of GSHEs. In the present study, the effects of the distance between boreholes, soil properties, grout heat conduction coefficient, and boreholes’ arrangement are investigated on the outlet fluid temperature in the GSHEs. The Finite Line Source (FLS) model is coupled with the Simplified Thermal Resistance-Capacity Model (STRCM) and a transient modified model called FLS-STRCM is developed. The FLS model considers the thermal interaction between boreholes while the STRCM model solves the flow field inside the boreholes. The obtained results of the FLS-STRCM are compared with the transient results of Computational Fluid Dynamics (CFD) simulations and available experimental data. To simulate the heating and cooling cycles of a building, the present model of GSHE is coupled with the water to air heat pump in the TRNSYS software. The available models of GSHEs in the TRNSYS software are not capable of considering different arrangements of boreholes. However, the present model, in addition to the transient simulation of GSHEs, can examine any desired layouts of boreholes. The results of the present model show that for a set of 6 boreholes in a rectangular arrangement, a reduction of the distance between boreholes from 7 m to 3 m results in 2.8% changes in the average temperature of outlet fluid. Also, the investigation of soil and grout properties shows that the soil properties has a dominant effect on the outlet fluid temperature. Considering the computational time and the acceptable accuracy of the presented model compared to the CFD methods, the FLS-STRCM model can be employed for the engineering applications in the construction of the GSHE system and the long-term simulations.

This research presents a numerical investigation of two-phase flow during the expulsion of entrapped air in a non-confined pipe. A modified version of the volume of fluid (VOF) approach is employed...

Radiant cooling panels are believed to be of considerable energy saving potentials and can be employed as new cooling devices in HVAC systems. Even though the popularity of radiant cooling systems grows, particularly for cooling and heating commercial buildings, the condensation problem limits their application. The present research is conducted to introduce and evaluate a new method to control the condensation problem in the Ceiling Radiant Cooling Panels (CRCP). A dehumidification coil is integrated with CRCP in order to regulate the water condensation and remove the latent heat load. To evaluate the capability of the new model, the performance of the system was numerically investigated in a sample office, for different wall insulation and room configurations. The results showed that the integrated cooling coils enhance the natural convection heat transfer and remove the water vapor from the space. Therefore, the condensation problem on the CRCPs could be solved using the introduced method. The thermal comfort calculated according to temperature and humidity distributions demonstrated that the new system has the ability to maintain comfort conditions. Moreover, the calculated cooling load to preserve thermal comfort is much lower in the introduced method compared to the conventional system. The comparison of cooling load between the new configuration and the conventional system exhibited the energy saving potential up to 30% in the new system.

Three-dimensional simulation of a multiphase flow is performed using the Eulerian-Eulerian finite volume method in order to evaluate the separation efficiency and velocity field of deoiling hydrocyclones. The solution is developed using a mass conservation-based algorithm (MCBA) with collocated grid arrangement. The mixture approach of the Reynolds stress model is also employed in order to capture features of turbulent multiphase swirling flow. The velocity field and separation efficiency of two different configurations of deoiling hydrocyclones are compared with available experimental data. The comparison shows that the separation efficiency can be predicted with high accuracy using computational fluid dynamics. The velocity fields are also in good agreement with available experimental velocity measurements. Special attention is drawn to swirl intensity in deoiling hydrocyclones and it is shown that the differences in velocity and volume fraction fields of different configurations are related to swirl distribution.

In this study, the effect of cone angle on the flow field and separation efficiency of deoiling hydrocyclones is investigated taking advantage of large eddy simulation. The dynamic Smagorinsky is employed to determine the residual stress tensor of the continuous phase. The method of Lagrangian particle tracking with an optimized search algorithm (closest cell) is applied to evaluate the separation efficiency of deoiling hydrocyclone. Simulations are performed on a 35-mm deoiling hydrocyclone with the three different cone angles of 6, 10 and 20 degree. The numerical results revealed that the changes in the cone angle would affect the velocity and pressure distribution inside hydrocyclone, and lead to changes in the separation efficiency. However, the large cone angle increases the tangential velocity and pressure gradient inside the hydrocyclone, but reduces the separation efficiency. The reasons behind the decrease in the separation efficiency are the flow structure and reduction of oil droplets residence time in hydrocyclones with large cone angles.

In order to evaluate the separation efficiency and flow field of deoiling hydrocyclones a three dimensional simulation is performed using large eddy simulation (LES) approach. Although this approach has been used in other types of hydrocyclones, the present work is a primer application of the LES approach for simulation of deoiling hydrocyclones. Due to anisotropic behavior of flow inside the hydrocyclones, LES is a suitable method to predict the flow field since it resolves large scales and models isotropic small scales. Obtained velocity field using the LES approach in comparison with other turbulence models is in good agreement with available experimental velocity measurements. The method of Lagrangian particle tracking with an optimized search algorithm (closest cell) is also used to evaluate the separation efficiency of deoiling hydrocyclones. Special attention is drawn to droplet drag coefficient, while the differences between separation efficiency curves using modified drag coefficient are also highlighted.

This research presents numerical simulation of the unsteady flow field inside the draft tube of a Kaplan turbine at part load condition. Due to curvature of streamlines, the ordinary two-equations ...