A municipality water reticulation R22 ground-coupled reversible heat pump, was investigated as an alternative to conventional air source systems. The investigation was conducted by developing analytical models that were used for the design of a ground-coupled reversible heat pump and a conventional, also reversible air-to-air system. The models were verified with a commercially available computer program as well as with measurements on the two systems.
Modelling thermal and aerial behaviour of unconditioned buildings requires an accurate knowledge of the air temperature and velocities fields inside the considered spaces. Furthermore, in ourMediterranean context, thermal and aerial aspects must be considered coupled together, because oftheir very strong interdependence. We have then developed a three-dimensional dynamic modularmodel of coupled heat transfer and airflow calculation.
The paper presents a method of designing thermal comfort conditions in a room with an UnderFloor Air Distribution system (UFAD). A two-phase algorithm is based on: a steady or unsteady heat and mass transfer theory in the first step of computation and thermal comfort calculation in the second step. This method is implemented as the computer program UFAD_NET.
This paper studies in three-dimension the coupled convective and radiative heat transfer rate from awindow surface with adjacent venetian blind using a commercial CFD code. For this study the window surface was modeled as an isothermal vertical flat plate. The flow patterns (temperature and velocity fields) and convective heat transfer coefficient were investigated for different blade angles (00, 450, -450, 800). Comparisons were made with experimental and other theoretical research.
We describe the flow in an underfloor plenum. We show that the geometry of the plenum causes the flow to exhibit two-dimensional dynamics and to develop flow patterns that are determined by the inlets of the underfloor into the plenum void. We describe laboratory experiments that simulate these flows and also show that the location and number of diffusers in the plenum has little effect on the underfloor flow. Depending on the location of the inlets to the plenum, the flow can exhibit complex vortex patterns and may be time dependent.
A comprehensive modelling of a compact double skin facade equipped with a venetian blind is proposed here. The modelling is done using CFD approach to asses the air movement inside the ventilated facade channel and appropriate radiation model for long and short wave exchanges. The impact of solar radiation on temperature and velocity fields as a function of some parameters such as beam radiation incidence angle, blade angle of solar protection, etc. is analysed.
This paper presents a simple model for vertical temperature profile and heat transfer predictionin displacement ventilation. The fully-mixed room air approximation that is currently used in most whole building analysis tools is extended to a three node approach, with the purpose of obtaining a first order precision model for displacement ventilation systems. The use of three nodes allows for improved prediction of thermal comfort and overall building energy performance in low energy cooling strategies that make use of unmixed stratified ventilation flows.
The assessment of the overall thermal insulation of the air shear layer surrounding a nude humanoid shape, as affected by different step rates, is the main objective of the present study. Step rateswere controlled at 0, 20, 30 and 45 steps/min. The measurements were carried out in a climate chamber with an articulated thermal manikin of the Pernille type with 16 body segments. In addition, the convective heat transfer coefficients for the 16 segments and for the whole body were determined for each step rate.
In the case of moderate climates, convective and radiative heat exchanges are the main avenues for heat losses on a human body. When using a dummy it is sometimes difficult to have a good estimation of the heat transfer coefficients for convection and/or radiation and especially to determine the part of each mode. It is now quite easy to calculate radiative transfer with accuracy. The approach proposed here, is to find a better estimation of the local radiative heat transfer through modeling and to discuss the value of local radiative coefficients in different situations.
This paper presents ventilation systems with longitudinal counterflow spiral recuperators. Heat transfer losses in ventilation system can be reduced by increasing the length of the recuperator, but in this case pressure drops increase. These two losses determine exploitation costs. Taking into consideration the results of measurements and calculations the costs for capital expenditure and exploitation of ventilation systems are minimized.
Login