Bjarne W. Olesen

Effect of physical activity and air velocity on the thermal insulation of clothing

Abstract Intrinsic thermal clothing insulation and surface air insulation were measured on human subjects by the use of indirect calorimetry. Four male clothing ensembles (0-1-1 -8 clo) and three female clothing ensembles (0-2-1-2 clo) were investigated. Using the standing position as a reference, the influence of sitting, bicycling (40r.p.m., 20 W), walking (3-75 km hour−1) and of light packing work on the thermal insulation was studied. The influence of an air velocity of 11ms−1 on thermal insulation during the standing and walking conditions was investigated. The results showed that: (i) intrinsic clothing insulation was maximal in the standing position. It was reduced by 8-18% in the seated position and by 30-50% during bicycling and walking. An air velocity of 11ms−1 did not influence the intrinsic clothing insulation during walking, but decreased it by 18% in the standing position; (ii) surface air insulation varied with activity and air velocity, but not with clothing. It was increased by up to 25%...

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.

The Mental Performance of Subjects Clothed for Comfort at Two Different Air Temperatures

Thirty-two subjects (16 male and 10 female students aged (8-25 yr) performed sedentary work in a climate chamber under two different conditions. The subject wore a light standard clothing (0.6 clo) on one occasion and a heavy clothing ensemble (1.5 clo) on the other. Each subject was exposed singly, for 2-5 hr on each occasion. During the exposures the air temperature was continuously adjusted up or down at the subjects request, as indicated on a dial voting apparatus, so that he remained in thermal comfort. Skin temperatures were measured throughout. Performance measures were obtained on a numerical addition task, a recognition memory task, and on a test of cue-utilization. Subjects rated their effort, arousal and fatigue, and the freshness of the air on semantic differential scales. No significant differences in performance could be shown between the two conditions. Subjective effort, arousal and fatigue did not differ, but subjects considered that the air was fresher in the cool air/heavy clothing con...

Criteria for the indoor environment for energy performance of buildings

Purpose – To provide input data to design and energy performance calculations of buildings and ventilation, heating, cooling and lighting systems.Design/methodology/approach – European directive for energy performance of buildings was approved in the beginning of 2003. The transition period is 3‐6 years depending on the article. European Standardisation Organisation (CEN) has drafted several standards to help the member countries implementing the directive. One of these is the “Criteria for the indoor environment including thermal, indoor air quality (ventilation) light and noise.” The standard has been developed based on existing international standards and guidelines for the indoor environment taken into account the latest results from published research.Findings – The standard specifies design values of indoor environment, values to be used in energy calculations, and methods how to verify the specified indoor environment in the buildings. The paper describes some of the principles used in standards, a...

Thermal energy storage—A review of concepts and systems for heating and cooling applications in buildings: Part 1—Seasonal storage in the ground

The use of thermal energy storage (TES) in buildings in combination with space heating and/or space cooling has recently received much attention. A variety of TES techniques have developed over the past decades. TES systems can provide short-term storage for peak-load shaving as well as long-term (seasonal) storage for the introduction of natural and renewable energy sources. TES systems for heating or cooling are utilized in applications where there is a time mismatch between the demand and the most economically favorable supply of energy. The selection of a TES system mainly depends on the storage period required, economic viability, and operating conditions. One of the main issues impeding the utilization of the full potential of natural and renewable energy sources, e.g., solar and geothermal, for space heating and space cooling applications is the development of economically competitive and reliable means for seasonal storage of thermal energy. This is particularly true at locations where seasonal variations of solar radiation are significant and/or in climates where seasonally varying space heating and cooling loads dominate energy consumption. This article conducts a literature review of different seasonal thermal energy storage concepts in the ground. The aim is to provide the basis for development of new intelligent TES possibilities in buildings.

Thermal comfort in commercial kitchens (RP-1469): Procedure and physical measurements (Part 1)

The indoor climate in commercial kitchens is often unsatisfactory, and working conditions can have a significant effect on employees’ comfort and productivity. The type of establishment (fast food, casual, etc.) and climatic zone can influence thermal conditions in the kitchens. Moreover, the size and arrangement of the kitchen zones, appliances, etc., further complicate an evaluation of the indoor thermal environment in commercial kitchens. In general, comfort criteria are stipulated in international standards (e.g., ASHRAE 55 or ISO EN 7730), but are these standardized methods applicable to such environments as commercial kitchens? This article describes a data collection protocol based on measurements of physical and subjective parameters. The procedure was used to investigate more than 100 commercial kitchens in the United States in both summer and winter. The physical measurements revealed that there is a large range of kitchens environments and confirmed that employees are exposed to a warm-to-hot environment. The measured ranges of activities and temperatures in many cases were outside the range recommended by ASHRAE 55 and ISO EN 7730. The study showed that the predicted mean vote/percentage people dissatisfied (PMV/PPD) index is not directly appropriate for all thermal conditions in commercial kitchens.

Experimental Study of Air Distribution and Ventilation Effectiveness in a Room with a Combination of Different Mechanical Ventilation and Heating/Cooling Systems

Abstract Mixing and displacement ventilation are common systems in commercial buildings, while mixing ventilation is used in residential buildings. Displacement ventilation provides fresh air to the occupied zone in a more efficient way than mixing ventilation but it is important to know how well it works with a floor system for heating or cooling. Can, for example, a floor heating system warm up the supply air too fast and destroy the displacement effect? Will floor cooling, combined with displacement ventilation, result in too high a vertical temperature difference and too low a temperature at feet level? The required amount of ventilation depends on the ventilation effectiveness. In standards, the recommended values for ventilation effectiveness depend on the position of the supply and exhaust device and on the difference between supply and room air temperature. Among others, for warm air heating the ventilation effectiveness is always less than 1 and can be as low as 0.4. This would then require an increased amount of ventilation. A combination of floor heating/cooling, radiators, air cooling, displacement ventilation, mixed ventilation and different combinations of supply and return grilles have, in this study, been experimentally tested. The studies on a displacement ventilation system show lower vertical air temperature differences and higher ventilation effectiveness when it is combined with a floor heating system. With floor cooling, the displacement ventilation system should be designed with a higher supply air temperature. Furthermore, the buoyancy flows from warm or cold windows and occupants influence the airflow pattern and increase the mixing of supply air into the occupied zone.

Floor Heating with Displacement Ventilation: An Experimental and Numerical Analysis

The effect of floor heating combined with displacement ventilation (DV) on thermal indoor environments and indoor air quality (IAQ) was studied by means of CFD. The numerical model was validated with experimental data. A typical office room was simulated, and one of the occupants was considered to be the contaminant source. The CFD model reliably simulated air velocities and temperatures. Also ventilation effectiveness values were coherent with experimental data. The model made it possible to understand the effect of the downdraft from a cold window on the dissemination of contaminant in the room. Although ventilation effectiveness at seated breathing height was always higher than one, it was not possible to visualize a defined contaminant stratification in the room. Only when the windows were not assumed to be cold, a clearly stratified flow pattern could be detected. The numerical model was then used to simulate different kinds of contaminant sources, under the same boundary conditions. It was found that DV does not guarantee a better IAQ than full mixing when contaminant sources are not linked to heat sources, even when floor heating is used. Contaminants produced by powerful heat sources require high ventilation flow rates to guarantee high values of ventilation effectiveness.

Evaluation of a vertical displacement ventilation system

Abstract The effectiveness of a vertical displacement ventilation system was evaluated when contaminants including tobacco smoke were present. Air supply was through a perforated floor and carpet. System performance was evaluated using ADPI (Air Diffusion Performance Index), percentage dissatisfied due to draft, vertical temperature difference, and air change, and contaminant removal indices. Gaseous contaminants were simulated with tracer gas. Cigarettes and occupants also generated particulates, CO 2 , CO, and TVOC (total volatile organic compounds). Several combinations of supply air flow rate and thermal loads were evaluated. The risk of draft was found to be negligible. The air change effectiveness for the room varied from 126 to 145% and the contaminant removal effectiveness for the occupied zone varied from 80 to 700%.

Experimental study including subjective evaluations of mixing and displacement ventilation combined with radiant floor heating/cooling system

Sixteen subjects evaluated the indoor environment in four experiments with different combinations of ventilation systems and radiant heating/cooling systems. In the first two tests, the simulated residential room was equipped either by a mixing ventilation system supplying warm air for space heating or by a combination of radiant floor heating and mixing ventilation system. The vertical air temperature distribution was more uniform for floor heating. The discomfort due to cold feet/lower legs was higher for warm air heating, but no significant difference in thermal perceptions between the two mixing ventilation systems was found. The next two tests simulated an office room during summer, ventilated and cooled either by a displacement ventilation system alone or by a displacement ventilation system combined with radiant floor cooling. Displacement ventilation combined with floor cooling had lower floor temperature, warmer supply air, and less homogeneous vertical temperature profile, but it did not result in thermal discomfort on feet/lower legs or discomfort due to a vertical air temperature difference higher than for a displacement ventilation system alone, where the floor temperature was higher, supply air cooler, and vertical temperature profile more uniform.