convection

The paper presents a numerical study on the airflow within a single-sided heated room with a large vertical opening, with and without interaction of an air curtain. The influence of temperature differences between the heated wall and the exterior on the inflow has been investigated. Also how an air curtain, with different inlet velocities and widths, affect the flow and thermal patterns in the room have been examined. The RNG k-e turbulence model is used for capturing the fluid flow and heat transfer in the building and through the opening.

A numerical investigation has been made on the effect of thermal and mass buoyancy forces on the development of laminar mixed convection between vertical parallel plates with uniform wall heat and mass fluxes. Some parameters such as velocity, temperature and concentration are presented and their incidence on heat and mass transfer between the plates is discussed for both positive and negative values of the buoyancy ratio. Results and discussions are presented.

This paper presents the modeling of convective flows based on lattice Boltzmann methods in combination with a large eddy turbulence model. The used example is complex and three-dimensional.

This paper considers an ideal naturally ventilated building model that allows a theoretical study of the effect of thermal mass associating with the non-linear coupling between the airflow rate and the indoor air temperature.The thermal mass number and the convective heat transfer air change parameter are suggested to account for the effect of thermal mass heat storage and convective heat transfer at the thermal mass surfaces. The new thermal mass number measures the capacity of heat storage, rather than the amount of thermal mass.

Two methods have been used for measurement of natural convection flows in a narrow vertical channel of which one wall is heated : a hot wire anemometer adapted to measurements in flows where temperature gradients exist (two hot wires with different overheat) and a method for attaining bulk flow information in boundary layer flows. Results from these two methods are compared.

A simple conceptual approach to room surface convective heat transfer is presented, defining a global room heat transfer coefficient. It is applied to two room ventilation systems : mixing and cross-ventilation.

16 segmental and all body heat transfer convective coefficients were determined in tests performed with a thermal mannequin placed in the test chamber of a large wind-tunnel.This paper presents a general table with the numerical coefficients of the equations representing the evolution of the convective coefficient with the flow velocity for all the studied cases (front, back and side flow - at seated and standing postures) . The effect of natural convection is more obvious on the central part of the body. Peripheric parts have stronger losses.

The aim of that study is to make a database of the local convective heat transfer coefficients for each part of a human body in sedentary and standing environments through the use of an experimental thermal manikin and an analysis of the radiative heat transfer rate. The results are applicable to both indoor and outdoor environments.

The paper also discusses the influences of wind velocity, sensible heat loss, posture and furniture arrangements on local convective heat transfer coefficients values.

Numerical modelling of convective air movements inside a heated room was built, using a coupling of a zonal model and integral analysis. The model describes the heat transfer between air and walls, between different air layers inside the room, between air in the room and cold air jet from ventilation air supply, and between air and heat emitter. Experiments were conducted in a testing chamber with floor heating or heating by a hot water radiator, with steps in hot water and ventilation flow rates. Validation results are satisfying.

Two-dimensional computational simulations are performed to examine the effect of vertical location of a convective heat source on thermal displacement ventilation systems. In this study, a heat source is modeled with seven different heights from the floor (0.5m, 0.75m, 1.0m, 1.25m, 1.5m, 1.75m, 2.0m) in a displacement ventilation environment. The flow and temperature fields in thermal displacement ventilation systems vary depending on the location of the heat source. As a heat source rises, the convective heat gain from the heat source to an occupied zone becomes less significant.