Assessment of thermal environment using a thermal manikin in a field environment chamber served by displacement ventilation system

This paper presents a thermal comfort study using a thermal manikin in a field environment chamber served by the Displacement Ventilation (DV) system. The manikin has a female body with 26 individually heated and controlled body segments. The manikin together with subjects was exposed to 3 levels of vertical air temperature gradients, nominally 1, 3 & 5 K/m, between 0.1 and 1.1 m heights at 3 room air temperatures of 20, 23 and 26 °C at 0.6 m height. Relative humidity at 0.6 m height and air velocity near the manikin and the subjects were maintained at 50% and less than 0.2 m/s, respectively. The aims of this study are to assess thermally non-uniform environment served by DV system using the manikin and correlate the subjective responses with measurements from the manikin. The main findings indicate that room air temperature had greater influence on overall and local thermal sensations and comfort than temperature gradient. Local thermal discomfort decreased with increase of room air temperature at overall thermally neutral state. The local discomfort was affected by overall thermal sensation and was lower at overall thermally neutral state than at overall cold and cool sensations.     

Observations of upper-extremity skin temperature and corresponding overall-body thermal sensations and comfort

This paper explores how upper extremity skin temperatures correlate with overall-body thermal sensation. Skin temperature measurements of the finger, hand, and forearm might be useful in monitoring and predicting people's thermal state. Subjective perceptions of overall thermal sensation and comfort were collected by repeated surveys, for subjects in a range of test chamber temperatures. A positive temperature gradient (finger warmer than the forearm) of as much as 2 K was seen when subjects felt warm and hot, while a negative temperature gradient (finger colder than the forearm) as much as 8.5 K was seen for cool and cold subjects. A useful warm/cold boundary of 30 °C was found in finger temperature, for both steady state and transient conditions. When finger temperature was above 30 °C, or finger-forearm skin temperature gradient above 0 K, there was no cool discomfort. When finger temperature was below 30 °C, or the finger-forearm skin temperature gradient less than 0 K, cool discomfort was a possibility. Finger temperature and finger-forearm temperature gradient are very similar in their correlation to overall sensation. We also examine how overall sensation is affected by actively manipulating the hand's temperature.     

Effect of stove asymmetric radiation field on thermal comfort using a multisegmented bioheat model

The multinode multisegment bioheat model of Salloum et al. [Salloum M, Ghaddar N, Ghali K. A new transient bio-heat model of the human body. In: Proceedings of the ASME 2005 summer heat transfer conference, 17–22 July 2005, San Francisco, Paper no. HT2005-72303] is integrated with a space heat model to study human thermal response when subjected to radiant asymmetry in stove-heated domestic spaces in Lebanon. For any given person position, the overall comfort level is based on Frank et al. model correlations [Frank SM, Srinivasa NR, Bulcao CF, Goldstein DS. Relative contribution of core and cutaneous temperatures to thermal comfort and autonomic responses in humans. Journal of Applied physiology 1999;86(5):1588–93]. The assessment of local comfort level is based on the maximum deviation of the clothed segments skin temperature from the mean skin temperature and its relation to the radiant temperature asymmetry.

Experiments were run on human subjects at steady-state conditions to measure the variation of the skin temperature at different locations of the human body segments while standing in an asymmetric thermal radiation field generated by a stove-heating unit. The experiments were conducted to validate the applicability of the bioheat model in predicting skin temperature in asymmetric conditions. The measured skin temperature of various body segments and the radiative asymmetry agreed within ±5% of values predicted by the bioheat model [Salloum M, Ghaddar N, Ghali K. A new transient bio-heat model of the human body. In: Proceedings of the ASME 2005 summer heat transfer conference, 17–22 July 2005, San Francisco, Paper no. HT2005-72303].

The space heat model and the bioheat model are applied to a case study to predict both overall thermal comfort and local thermal discomfort in a typical radiant heat space at different standing positions of the person. Strong thermal discomfort exists within the vicinity of the stove high-temperature surface. The local discomfort is considered at values of maximum SD>1.1 °C derived from consideration of Fanger et al. [Fanger PO, Ipsen BM, Langkilde G, Olesen BW. Comfort limits for asymmetric thermal radiation. Energy and Buildings 1985;8(3):225–36] data of comfort limits and skin temperature measurements for asymmetric thermal radiation.     

Evaluation of comfort level in desks equipped with two personalized ventilation systems in slightly warm environments

In this work the comfort level, namely the thermal comfort, local thermal discomfort and air quality levels, in a classroom with desks equipped with two personalized ventilation systems, in slightly warm environments, is evaluated. A manikin, a ventilated classroom desk, two indoor climate analyzers, a multi-nodal human thermal comfort numerical model and a computational fluid dynamic numerical model, are used.     

Local thermal sensation and comfort study in a field environment chamber served by displacement ventilation system in the tropics

This paper presents a study of local thermal sensation (LTS) and comfort in a field environmental chamber (FEC) served by displacement ventilation (DV) system. The FEC, 11.12 m (L)×7.53 m (W)×2.60 m (H), simulates a typical office layout. A total of 60 tropically acclimatized subjects, 30 male and 30 female, were engaged in sedentary office work for 3 h. Subjects were exposed to three vertical air temperature gradients, nominally 1, 3 and 5 K/m, between 0.1 and 1.1 m heights and three room air temperatures of 20, 23 and 26 °C at 0.6 m height. The objective of this study is to investigate the mutual effect of local and overall thermal sensation (OTS) and comfort in DV environment. The results show that in a space served by DV system, at OTS close to neutral, local thermal discomfort decreased with the increase of room air temperature. The OTS of occupants was mainly affected by LTS at the arm, calf, foot, back and hand. Local thermal discomfort was affected by both LTS and OTS. At overall cold thermal sensation, all body segments prefer slightly warm sensation. At overall slightly warm thermal sensation, all body segments prefer slightly cool sensation.     

Thermal pleasure in built environments: spatial alliesthesia from contact heating

The comfort zone is bounded by thermal environmental conditions that may be described as acceptably cool or acceptably warm, and engineering out of existence these innocuous thermal conditions on the fringes of the adaptive comfort range may not be necessary. In contrast to the conventional understanding of local discomfort, spatial alliesthesia exploits corrective differences in the rate of change in skin temperature between individual body segments to elicit positive affective sensations. This paper examines reverse instances of local discomfort, or spatial alliesthesia, from warm contact stimuli applied to hand and feet when exposed to ambient conditions towards the lower margin of the comfort zone. It was found that subjects with moderate feelings of displeasure or even indifference were still capable of experiencing a pleasant response to localized thermal stimuli. Brief whole-body thermal pleasure was observed from in-situ skin temperature changes at a single distal body site. These effects were subtle and not universally experienced, so the success of their deliberate implementation in built environments depends heavily on some form of individual control. Spatial alliesthesia therefore complements the body of literature investigating personal environmental control and local thermal discomfort by providing a theoretical framework of thermal perception in non-neutral environments.     

Thermal comfort evaluation with virtual manikin methods

Computational fluid dynamics has become an important tool in the prediction of thermal comfort in occupied spaces. Despite its ability to predict temperature and velocity fields, it is more difficult to evaluate the degree of thermal comfort experienced by an occupant. This article describes the construction of a new numerical thermal manikin, with new comfort evaluation methods based on data from thermal manikin measurements as well as subjective results from several hundred experiments. The level of thermal comfort is highly dependent on the local environment. Human beings respond differently to local heat transfer in different parts of their bodies. It is suggested for that reason that local results from manikins should be presented in new clothing independent comfort zone diagrams. The research presented in here is intended to be used to evaluate system solutions that provide improved thermal climate in many different everyday situations, e.g. all types of buildings and vehicles.     

Experimental investigation into the interaction between the human body and room airflow and its effect on thermal comfort under stratum ventilation

Room occupants' comfort and health are affected by the airflow. Nevertheless, they themselves also play an important role in indoor air distribution. This study investigated the interaction between the human body and room airflow under stratum ventilation. Simplified thermal manikin was employed to effectively resemble the human body as a flow obstacle and/or free convective heat source. Unheated and heated manikins were designed to fully evaluate the impact of the manikin at various airflow rates. Additionally, subjective human tests were conducted to evaluate thermal comfort for the occupants in two rows. The findings show that the manikin formed a local blockage effect, but the supply airflow could flow over it. With the body heat from the manikin, the air jet penetrated farther compared with that for the unheated manikin. The temperature downstream of the manikin was also higher because of the convective effect. Elevating the supply airflow rate from 7 to 15 air changes per hour varied the downstream airflow pattern dramatically, from an uprising flow induced by body heat to a jet‐dominated flow. Subjective assessments indicated that stratum ventilation provided thermal comfort for the occupants in both rows. Therefore, stratum ventilation could be applied in rooms with occupants in multiple rows.     

Investigation of indoor thermal comfort under transient conditions

In industrialized countries about 90% of the time is spent indoors. In indoor, thermal comfort can be basically predicted by the environmental parameters such as temperature, humidity, air velocity and by the personal parameters as activity and clothing resistance. In this study, a mathematical model of thermal interaction between human body and environment was established and the effect of clothing and air velocity was examined under transient conditions. By the developed model, human body has been separated to 16 segments and possible local discomforts are taken into consideration. Using the model, changes in the sensible and latent heat losses, skin temperature and wettedness, thermal comfort indices were calculated. In a hot environment latent heat loss increases by means of sweating. Because of over wetted skin, comfort sense goes worse. Especially, at feet and pelvis skin wettedness reaches maximum level. Sensible and latent heat losses rise and the skin temperature and wettedness decrease with increasing air velocity.     

Evaluation of calculation methods of mean skin temperature for use in thermal comfort study

A method was established to evaluate calculation methods of mean skin temperature, in order to find appropriate ones for use in human thermal comfort study. In this method three indexes, including reliability, sensitivity and number of measurement sites, were proposed. Under air temperatures of 21 °C, 24 °C, 26 °C, and 29 °C, 22 subjects’ local skin temperatures (21 sites) and electrocardiograms were measured, and their thermal sensation and thermal comfort were inquired. Human heart rate variability indicated the physiological relation between mean skin temperature and ambient temperature for the sensitivity evaluation. Adopting the evaluation method, 26 types of mean skin temperature calculation methods were evaluated based on the experimental data. The results indicate that a calculation method of mean skin temperature with 10 sites is the most appropriate one, due to its high reliability, excellent sensitivity and fewer measuring sites. When it was applied to reflect thermal comfort, the performance was good.     

A field study of occupant thermal comfort and thermal environments with radiant slab cooling

This paper presents the findings of a field study of occupant thermal comfort and thermal environments with a radiant slab cooling system. The study combined field measurements and questionnaires based on the ASHRAE RP-921 project protocol. A total of 116 sets of data from 82 participants were collected in summer and winter. The results reveal that occupant whole-body thermal sensations with radiant cooling were consistent with the PMV model. The main advantage of radiant cooling for thermal comfort was found to be reduced local thermal discomfort with reduced vertical air temperature difference as well as reduced draft rate. The survey results revealed that 14–22% of participants in the study reported local cold discomfort in the arm–hand and the leg–foot regions. The results indicated that there may be lower limits on air speeds acceptable to occupants. Statistical analysis indicated that occupant thermal votes were free of significant correlation with personal, contextual and psychological factors. Suggestions to improve the questionnaire and the field survey process are offered.     

Discomfort due to Vertical Thermal Gradients

Abstract Abstract When 207 subjects wearing their own clothing were randomly assigned to 9 conditions, consisting of 3 levels of vertical thermal gradient (nominally 0, 2 & 4 K/m), and 3 levels of estimated whole-body heat loss (40, 48 & 56 W/m² as measured on a similarly-clothed and seated thermal manikin, corresponding to warm, neutral and cool conditions respectively, “warm” being 1.4 K above neutral in terms of operative temperature, and “cool” being 1.4 K below) and exposed for 1 hour, local thermal discomfort was reported by 45% of the group. Local and whole-body discomfort sensations were unaffected by thermal gradient (P>0.30), but were strongly affected by operative temperature (P<0.001). Discomfort due to dry air was unaffected by thermal gradient (P>0.30), but increased significantly with operative temperature (P<0.001). Discomfort due to dry eyes increased significantly above 2 K/m (P<0.01), but was unaffected by operative temperature (P>0.80). Individual differences in thermal and air quality requirements are shown to be sufficient to cause the thermal discomfort associated with thermal gradients up to 4 K/m.     

Numerical analysis of air flow, heat transfer, moisture transport and thermal comfort in a room heated by two-panel radiators

A three-dimensional steady-state numerical analysis was performed in a room heated by two-panel radiators. A virtual sitting manikin with real dimensions and physiological shape was added to the model of the room, and it was assumed that the manikin surfaces were subjected to constant temperature. Two different heat transfer coefficients for the outer wall and for the window were considered. Heat interactions between the human body surfaces and the room environment, the air flow, the temperature, the humidity, and the local heat transfer characteristics of the manikin and the room surfaces were computed numerically under different environmental conditions. Comparisons of the results are presented and discussed. The results show that energy consumption can be significantly reduced while increasing the thermal comfort by using better-insulated outer wall materials and windows.     

Thermal sensation and comfort models for non-uniform and transient environments, part III: Whole-body sensation and comfort

A three-part series presents the development of models for predicting the local thermal sensation (Part I) and local thermal comfort (Part II) of different parts of the human body, and also the whole-body sensation and comfort (Part III) that result from combinations of local sensation and comfort. The models apply to sedentary activities in a range of environments: uniform and non-uniform, stable and transient. They are based on diverse findings from the literature and from body-part-specific human subject tests in a climate chamber. They were validated against a test of automobile passengers. The series is intended to present the models’ rationale, structure, and coefficients, so that others can test them and develop them further as additional empirical data becomes available.A) The whole-body (overall) sensation model has two forms, depending on whether all of the body's segments have sensations effectively in the same direction (e.g warm or cool), or whether some segments have sensations opposite to those of the rest of the body. For each, individual body parts have different weights for warm versus cool sensations, and strong local sensations dominate the overall sensation. If all sensations are near neutral, the overall sensation is close to the average of all body sensations.B) The overall comfort model also has two forms. Under stable conditions, people evaluate their overall comfort by a complaint-driven process, meaning that when two body parts are strongly uncomfortable, no matter how comfortable the other body parts might be, the overall comfort will be near the discomfort level of the two most uncomfortable parts. When the environmental conditions are transient, or people have control over their environments, overall comfort is better than that of the two most uncomfortable body parts. This can be accounted for by adding the most comfortable vote to the two most uncomfortable ones.     

Effects of radiant temperature on thermal comfort

The aim of this paper is to investigate the local differences between body segments caused by high radiant temperature, and to analyze the interior surface temperatures for different wall and ceiling constructions with their effect on thermal comfort. For the segment-wise thermal interactions between human body and its surrounding, simulations have been conducted by appropriately modifying Gagge 2-node model to multi-segment case to demonstrate the local differences. Simulation results are found to be in good agreement with experimental and simulation results reported in the literature. To calculate the interior surface temperatures of the wall and ceiling, the sol–air temperature approach is used for convenience. It is shown in the paper that the body segments close the relatively hot surfaces are more affected than others and interior surface temperatures of un-insulated walls and ceilings exposed to a strong solar radiation reach high levels, all of which cause thermal discomfort for the occupants in buildings.     

Neutral temperature in subtropical climates—A field survey in air-conditioned offices

The thermal environment for air-conditioned offices in subtropical climates is examined from the prospect of maintaining an optimum operative temperature for the occupants. In this study, the optimum neutral temperature is evaluated from 422 occupants’ responses towards the perceiving thermal environment in 61 air-conditioned offices and 186 complaints of thermal discomfort in an air-conditioned office building on an electronic questionnaire, using a semantic differential evaluation scale and a dichotomous assessment scale. In particular, physical parameters for the thermal comfort study were measured by an indoor environmental quality (IEQ) logger, and the operative temperature was correlated with the occupants’ thermal responses. The probability of accepting an operative temperature for the thermal comfort of the occupants was correlated with logistic regression curves; the optimum operative temperature was derived in order to maximize the probability of thermal comfort expressed by the occupants. The results showed that the thermal neutral temperatures for air-conditioned offices in subtropical climates were 23.6 and 21.4 °C in summer and winter, respectively. The preferred thermal environment in Hong Kong should be slightly cool, corresponding to about 1 °C below the neutral temperature, in order to satisfy most of the occupants in the office space.     

Design considerations with ventilation-radiators: Comparisons to traditional two-panel radiators

Performance of heat emitters in a room is affected by their interaction with the ventilation system. A radiator gives more heat output with increased air flow along its heat transferring surface, and with increased thermal difference to surrounding air. Radiator heat output and comfort temperatures in a small one-person office were studied using different positions for the ventilation air inlet. In two of the four test cases the air inlet was placed between radiator panels to form ventilation-radiator systems. Investigations were made by CFD (Computational Fluid Dynamics) simulations, and included visualisation of thermal comfort conditions, as well as radiator heat output comparisons. The room model was exhaust-ventilated, with an air exchange rate equal to what is recommended for Swedish offices (7 l s⁻¹ per person) and cold infiltration air (−5 °C) typical of a winter day in Stockholm.Results showed that under these conditions ventilation-radiators were able to create a more stable thermal climate than the traditional radiator ventilation arrangements. In addition, when using ventilation-radiators the desired thermal climate could be achieved with a radiator surface temperature as much as 7.8 °C lower. It was concluded that in exhaust-ventilated office rooms, ventilation-radiators can provide energy and environmental savings.     

Thermal sensation and comfort models for non-uniform and transient environments: Part I: Local sensation of individual body parts

A three-part series presents the development of models for predicting the local thermal sensation (Part I) and local comfort (Part II) of different parts of the human body, and also the whole-body sensation and comfort responses (Part III). The models predict these subjective responses to the environment from thermophysiological measurements or predictions (skin and core temperatures). The models apply to a range of environments: uniform and non-uniform, transient and stable. They are based on diverse results from the literature and from body part-specific human subject tests in a climate chamber. They were validated against a test of passengers in automobiles. This series is intended to present the rationale, structure, and coefficients for these models so that others can test and develop them further as additional empirical data becomes available. The experimental methods and some measured results from the climate chamber tests have been published previously.Part I describes thermal sensation models representing 19 individual local body parts. The models' structure and coefficients were derived by regression of skin and core temperatures against thermal sensation votes obtained in the chamber experiments. The sensation for each local body part is predicted by a logistic function with four inputs: local skin temperature, mean-skin temperature presenting the whole-body thermal state, and the time derivatives of skin and core temperatures representing the response to transients. These inputs can be obtained from thermophysiological computer programs that treat the body as multiple segments.     

Models of human thermoregulation and the prediction of local and overall thermal sensations

This study aims at comparing the predictions of skin temperature from different models of human thermoregulation and investigating the currently available methods for the prediction of the local and overall thermal sensations. In this paper, the Fiala model, the University of California, Berkeley (UCB) thermoregulation model and a multi-segmental (MS) Pierce model were tested against recently measured data from the literature. The local and overall thermal sensations were predicted for different room conditions, obtained from a recent experimental study, using the UCB comfort model coupled with the MS-Pierce model. The overall thermal sensation was further predicted using three other models. The predictions were then compared with the subjective votes obtained from that study. The equivalent temperature approach was also investigated based on the same experimental study. The results show comparisons of the predicted skin temperature by the thermoregulation models, under steady state and dynamic conditions, with the measured data as well as the predictions of the thermal sensations from the different models.     

Measured radiant thermal fields in industrial spaces served by high intensity infrared heater

Work stations in industrial spaces are frequently arranged at a significant distance from each other. Local heating applying, among others, the gas-fired direct radiant heaters, is a viable alternative to the central heating. Radiant heaters provide heat comfort to workers and guarantee the maintenance of higher temperatures of the surrounding walls at a lower indoor temperature. The advantage of heating by gas-fired radiant heaters is the lower operational cost comparing to another systems. It uses less energy to obtain 2-3 K lower indoor temperature than in case of heating by conventional systems.The radiant temperature at work stations should be high enough to eliminate thermal discomfort, which in particular, is a result of radiant temperature asymmetry that may be caused by excessive and asymmetric overheating of the human body by a radiant heater.This paper includes formulas, based on the results of the self-designed test, which are then used in the calculation of the radiant temperature and the radiant temperature asymmetry, depending on the radiant heater position and the indoor temperature.This paper presents also the most recognized interrelations between the radiant temperature and its asymmetry. The discussed parameters are particularly significant in the heating process using high-temperature radiant heaters.