de Mh Martin Wit

Differences between young adults and elderly in thermal comfort, productivity, and thermal physiology in response to a moderate temperature drift and a steady-state condition.

UNLABELLED Results from naturally ventilated buildings show that allowing the indoor temperature to drift does not necessarily result in thermal discomfort and may allow for a reduction in energy use. However, for stationary conditions, several studies indicate that the thermal neutral temperature and optimum thermal condition differ between young adults and elderly. There is a lack of studies that describe the effect of aging on thermal comfort and productivity during a moderate temperature drift. In this study, the effect of a moderate temperature drift on physiological responses, thermal comfort, and productivity of eight young adults (age 22-25 year) and eight older subjects (age 67-73 year) was investigated. They were exposed to two different conditions: S1-a control condition; constant temperature of 21.5 degrees C; duration: 8 h; and S2-a transient condition; temperature range: 17-25 degrees C, duration: 8 h, temperature drift: first 4 h: +2 K/h, last 4 h: -2 K/h. The results indicate that thermal sensation of the elderly was, in general, 0.5 scale units lower in comparison with their younger counterparts. Furthermore, the elderly showed more distal vasoconstriction during both conditions. Nevertheless, TS of the elderly was related to air temperature only, while TS of the younger adults also was related to skin temperature. During the constant temperature session, the elderly preferred a higher temperature in comparison with the young adults. PRACTICAL IMPLICATIONS Because the stock of fossil fuels is limited, energy savings play an important role. Thermal comfort is one of the most important performance indicators to successfully apply measures to reduce the energy need in buildings. Allowing drifts in indoor temperature is one of the options to reduce the energy demand. This study contributes to the knowledge concerning the effects of a moderate temperature drift and the age of the inhabitants on their thermal comfort.

The influence of local effects on thermal sensation under non-uniform environmental conditions - Gender differences in thermophysiology, thermal comfort and productivity during convective and radiant cooling

Applying high temperature cooling concepts, i.e. high temperature cooling (T(supply) is 16-20°C) HVAC systems, in the built environment allows the reduction in the use of (high quality) energy. However, application of high temperature cooling systems can result in whole body and local discomfort of the occupants. Non-uniform thermal conditions, which may occur due to application of high temperature cooling systems, can be responsible for discomfort. Contradictions in literature exist regarding the validity of the often used predicted mean vote (PMV) index for both genders, and the index is not intended for evaluating the discomfort due to non-uniform environmental conditions. In some cases, however, combinations of local and general discomfort factors, for example draught under warm conditions, may not be uncomfortable. The objective of this study was to investigate gender differences in thermophysiology, thermal comfort and productivity in response to thermal non-uniform environmental conditions. Twenty healthy subjects (10 males and 10 females, age 20-29 years) were exposed to two different experimental conditions: a convective cooling situation (CC) and a radiant cooling situation (RC). During the experiments physiological responses, thermal comfort and productivity were measured. The results show that under both experimental conditions the actual mean thermal sensation votes significantly differ from the PMV-index; the subjects are feeling colder than predicted. Furthermore, the females are more uncomfortable and dissatisfied compared to the males. For females, the local sensations and skin temperatures of the extremities have a significant influence on whole body thermal sensation and are therefore important to consider under non-uniform environmental conditions.

ELAN - A computer model for building energy design

Abstract A simplified thermal network model (ELAN) is developed for the assessment of thermal comfort and energy consumption for heating and cooling of a building. Each zone is modelled by a second order network with two temperature nodes which, for a multizone building, are linked by internal transmission and ventilation. The model can be solved on an hourly basis. ELAN has the flexibility of large models concerning geometry, number of zones, occupancy pattern, ventilation, plant operation and weather data.

High performance passive solar heating system with heat pipe energy transfer and latent heat storage modules

The aim of the project is to develop a passive solar heating system with a higher eficiency than conventional concrete thermal storage walls regarding accumulation and transfer of solar heat into dwellings and with restricted extra costs for manufacturing the system.

A Procedure to Measure the Diffusion Coefficient of Water in Brick as a Function of the Water Concentration

A procedure to measure the diffusion coefficient of water in brick as a function of the water concentration has been proposed, based on a method of measuring the mass of a drying brick at both outer ends. In this method, the brick is subjected to one-dimensional drying. The procedure was tested using a simulation with realistic parameter values and experimental inaccuracies. An experiment consisted of 120 s of drying and measuring the masses every 10 s with an accuracy of 10−6 kg. The sample was first dried to a lower water content and the drying was stopped for some time to allow the concentration profile to approximate a known equilibrium concentration profile, after which another measurement was performed at that lower water content. Minimizing the differences between the masses, as measured and as it follows from the model, gave the value of the diffusion coefficient. The method failed for low water concentrations.

Simple air collectors for preheating fresh air

In dwellings with mechanical ventilation systems the fresh air can easily be preheated by means of simple solar air systems. These can be an integral part of the building facade or roof and the costs are expected to be low. By means of computer experiments a large number of systems were evaluated. It was found that these systems can provide interesting energy gains providing the system is well dimensioned and has a storage. For this massive airducts are more effective than a massive absorber.

High Performance Passive Solar Heating System with Heat Pipe Energy Transfer

The aim of the project is to develop a passive solar heating system with a higher efficiency (regarding accumulation and transfer of solar heat into dwellings) than convential concrete thermal storage walls and with restricted extra costs for manufacturing the system. This is to be achieved by the introduction of three special components: a. a heat pipe as a thermal diode tube for efficient transfer of collected solar heat from the absorber to the back of an insulation layer b. a heat storage section with water or phase-change material c. an extra insulation sheet with vents between the storage and the room for controlled transfer of heat into the room.

Performance of passive solar systems in Dutch low-rise housing

Purpose of the work: The aim of the study is to determine the performance of passive solar systems in Dutch mass-housing under realistic conditions with a view to shading, density, urban tissue and dwelling lay-out.

On the application of the Bhatnagar-Gross-Krook model for a binary gas mixture

Abstract The Bhatnagar-Gross-Krook (B.G.K.) model for a binary gas mixture contains three unknown parameters. For a particular application these parameters can be found by comparison of the B.G.K. solution with a known solution of the Boltzmann equation for the problem under consideration. In this paper the hydrodynamic solution, obtained according to the Chapman-Enskog procedure, is used as such. Relations are derived between the unknown parameters of the B.G.K. model and the transport coefficients following from the hydrodynamic solution.