Showing papers on "Thermal comfort published in 1989"

Extending the summer comfort envelope with ceiling fans in hot, arid climates

Abstract: The purpose of this study was to determine if the summer comfort zone, as given in ASHRAE Standard 55-1981 could be expanded to include conditions obtained in hot, dry climates with a combination of evaporative cooling and the air motion obtained with ceiling fans. This study was conducted on 96 human subjects in the spring of 1986 and attempted to determine the upper limits of the comfort envelope (not just along the 50% RH line) with the higher velocities attained with ceiling fans. This study also suggests that the upper comfort limit proposed by Rohles et al. (1983) may be extended for humidities lower than 50% RH, but reduced for higher humidities

Local thermal discomfort due to draft and vertical temperature difference in rooms with displacement ventilation

Abstract: The paper evaluates the thermal comfort conditions in 18 spaces in practice ventilated by the displacement ventilation principle recently developed in Scandinavia. The risk of local discomfort due to draft and vertical temperature difference is estimated by comprehensive measurement of mean velocity, turbulence intensity, and air temperature. The results indicate a high risk of draft and vertical temperature difference in the occupied zone of some of the spaces. The draft risk and vertical temperature difference varied substantially within the occupied zone. They may create serious complaints in the half of the occupied zone nearest to the outlets. In several cases there was a potential risk of combined discomfort due to draft and vertical temperature difference. This combined discomfort should be studied by subjective experiments.

Methods for measuring and evaluating the thermal radiation in a room

Abstract: The mean radiant temperature is the parameter used to describe the influence of thermal radiation on man's general thermal comfort. The plane radiant temperature is then used to describe the asymmetry of the radiant environment. This paper will present and discusses several methods to measure or estimate these two factors. A comparison is made between different methods to measure the mean radiant temperature (globe-thermometer, ellipsoid-shaped sensor, plane radiant temperature in six directions, estimation by means of surface temperature, and angle factors). This comparison is made for three typical rooms representing residential buildings, office rooms, and industrial workplaces

The new comfort equation for indoor air quality

Abstract: A new philosophy of ventilation is introduced. The philosophy is quantified in a new comfort equation for indoor air quality based on the new units olf and decipol. The comfort equation prescribes the ventilation required to obtain a desired perceived air quality (in decipol) and in space with a given pollution load (in olfs). The comfort equation acknowledges for the first time all pollution sources, not just human bioeffluents and smoking, and it quantifies for the first time the quality of indoor and outdoor air as perceived by human beings. The equation prescribes more ventilation than present standards, or a reduction of the hidden olfs ruining the ir quality in many existing buildings. The comfort equation establishes a rational basis for future ventilation standards.

Application of radiant heating saves energy

Abstract: Application of radiant principles is one of the best kept secrets of the 20th century. The purpose of this application can reduce energy requirements. The theory of energy release from a high temperature surface was first proposed as a commercial product in the early 1900s. This article provides an understanding of how transfer or radiant energy works, identifies the factors that contribute to its economical performance and demonstrates how applications of radiant heating can provide comfort with lower energy costs.

A method for the optimal comfort and efficiency control of variable speed heat pumps and air conditioners

Abstract: A controller and a related method that maintains thermal comfort in an occupied space at a user-defined level while simultaneously maximizing the efficiency of the space conditioning equipment. The controller determines the setting of heating/cooling capacity, indoor airflow rate, evaporator superheat and other system parameters such that a comfort constraint is satisfied. The comfort index may be any arbitrarily-defined relationship of measured or inferred quantities such as air temperature, relative humidity, air velocity, mean radiant temperature, CO2 concentration, etc. The controller ensures that the error between comfort index and the comfort setpoint is zero while the energy consumed by the space conditioning equipment is minimized.

A study of heat transfer through clothing assemblies

Abstract: The work presented in this thesis is devoted to further understanding heat transfer through clothing under different circumstances, in order to provide guidelines for the design and construction of clothing with regard to thermal comfort. In one part of this work, studies were concentrated on the clothing thermal insulation in windy conditions. In this part, a newly designed cylindrical togmeter and a theoretical model have been developed. The numerical solution derived from the theoretical model agrees well with the experimental findings from the cylindrical togmeter in a wind tunnel. The heat transfer mechanisms involved in the wind induced reduction of clothing thermal insulation have been better understood by examining the experimental and theoretical results. The effects of wind velocity, air permeability and stiffness of the outer fabrics, air permeability and thickness of the inner fibrous battings, and the dimensions of the human body on the clothing thermal insulation have also been examined and discussed. Furthermore, based on the understanding of the mechanism of air penetration into permeable clothing assemblies, methods have been proposed for the design and construction of wind resistant protective clothing by using permeable outer fabrics. These methods were evaluated on the cylindrical togmeter and are believed to have important practical values. The other part of this work was focused on the development and laboratory use of a fabric manikin. The "skin" of the manikin was made of coated water-proof fabric, and heated water was circulated inside the "body". The arms and legs of the manikin could be moved to simulate walking. The manikin was very cheap to construct when compared with that of a copper manikin and can be widely applied for routine tests for outdoor and military garments subject to some modifications in its design. With this fabric manikin, a series of experiments have been conducted to investigate the effects of body motion, clothing design and environmental conditions on the thermal insulation of clothing. Some useful information for the design of functional clothing and for the prediction of the thermal stress of a clothed person in different environmental conditions has been provided through this investigation.

The MRT-correction method: a new method of radiant heat exchange

Abstract: This paper demonstrates that a new method of radiant heat exchange produces significantly improved accuracies over the BLAST and NBSLD loads programs. It incorporates the «mean radiant temperature (MRT) method», which is currently employed by the BLAST loads program. It is proposed that, with error analysis and numerical methods correction, components can be applied to the MRT algorithms. The correction components account for an enclosed environment's surface-to-surface exact angle factors, which are lacking in the MRT method. The new method will improve the accuracy of the MRT method while maintaining its advantageous computational time. This leads to accurate determination of building loads and human comfort conditions. The new method is most applicable to complex geometries and geometries with large surface temperature variations

Indoor climate — CIB W77

Abstract: Dr.‐Ing. Erhard Mayer of the Fraunhofer‐Institut fur Bauphysik, FhG (Director Prof. Dr.‐Ing. habil. Karl A. Gertis) has established that the indoor climate analyzer or artificial skin has proved useful for the objective evaluation of air movement for degrees of turbulence above 20%, and that the convective heat transfer coefficient, instead of mean air velocity, can be used as a basis for thermal comfort.

[Evaluation of thermal comfort in a student population: predictive value of an integrated index (Fanger's predicted mean value].

Abstract: Practical applications and predictive values of a thermal comfort index (Fanger's PRV) were verified on a sample school population (1236 subjects) by studying the relationships between thermal sensations (subjective analysis), determined by means of an individual questionnaire, and the values of thermal comfort index (objective analysis) obtained by calculating the PMV index individually in the subjects under study. In homogeneous conditions of metabolic expenditure rate and thermal impedence from clothing, significant differences were found between the two kinds of analyses. At 22 degrees C mean radiant and operative temperature, the PMV values averaged 0 and the percentage of subjects who experienced thermal comfort did not exceed 60%. The high level of subjects who were dissatisfied with their environmental thermal conditions confirms the doubts regarding the use of the PMV index as a predictive indicator of thermal comfort, especially considering that the negative answers were not homogeneous nor attributable to the small thermal fluctuations (less than 0.5 degree C) measured in the classrooms.