COMPARISON OF MATHEMATICAL MODELS FOR HEAT EXCHANGERS OF UNCONVENTIONAL CHP UNITS

An unconventional CHP unit with a hot air engine is designed as the primary energy source with fuel in the form of biomass. The heat source is a furnace designed for combustion of biomass, whether in the form of wood logs or pellets. The transport of energy generated by the biomass combustion to the working medium of a hot-air engine is ensured by a special heat exchanger connected to this resource. The correct operation of the hot-air engine is largely dependent on an appropriate design of the exchanger. The paper deals with the calculation of the heat exchanger for the applicationsmentioned, using criterion equations, and based on CFD simulations

CFD modeling of a high enthalpy geothermal context

The promising development of highly energetic geothermal resources could considerably enhance geothermal power production worldwide. The first attempt at tapping supercritical/heated fluids was made by the Iceland Deep Drilling project (IDDP), but unfortunately a magma layer at a depth of 2,100m was encountered, and the drilling was abandoned. Yet, this drilling operation failure generated new opportunities for assessing the potential power generation close to shallow magmatic intrusions. Detailed numerical methods are required to assess the heat transfer and fluid thermodynamics at wellbore and reservoir scale at near supercritical conditions to provide production scenarios and forecasts as accurate as possible. A primary steady-state study of reservoir and wellbore heat extraction from a geothermal well near a magmatic chamber has been performed with Computational Fluid Dynamics (CFD) techniques. Using simplified geological assumptions based on the IDDP-1 well description, a 2D axisymmetric single phase flow model was developed and its results were compared to those obtained with a full 3D CFD model. The simulated output power simulations reached 25 MW at 350°C and a wellhead pressure of 140 bars. Methodology and results from this study show that CFD techniques can be successfully used to assess geothermal energy outputs for unconventional geothermal wells and can provide details of a vapor superheated flow structure at wellbore-reservoir scale

Parametric Study of Vertical Ground Loop Heat Exchangers for Ground Source Heat Pump Systems

We report on a numerical study conducted to investigate the effect of various parameters on the heat exchange inside a vertical ground loop heat exchanger (VGLHE) for a ground-source heat pump (GSHP) system. The simulations were conducted for three piping configurations of the ground loop which were U-Tube, Concentric pipes and Spiral. The results show a linear temperature rise along the pipe length for the U-Tube configuration. The Concentric pipes configuration shows two distinct linear trends for the temperature rise; a slow temperature rise during the downward flow through the inner pipe and a higher temperature rise during the upflow through the annulus. The Spiral configuration shows a steeper slope for the temperature rise in the spiral section and almost a flat slope for the temperature rise in the straight vertical section of the pipe. The research also examines a simulation case of integrating a VGLHE inside of a micro-pile foundation system