Omer Kaynakli

Evaluating thermal environments for sitting and standing posture

The human thermal environment can be represented by the air temperature, radiant temperature, air velocity, humidity, clothing and activity. This has implications for health, comfort and performance. An understanding of human thermoregulatory processes facilitates the design and development of improved heating and cooling systems. This study presents a computational model of thermal interactions between a human and the interior environment. The model is based on the heat balance equation for human body with different types of clothing ensembles, combined with empirical equations defining the sweat rate and mean skin temperature. Simulation has been performed by the use of steady state conditions, and two different posture positions, namely sitting and standing, are considered in this study. Results are in good agreement with available experimental data. The parametric studies show that the methodology described can provide an effective means for simulating thermal comfort level.

Investigation of Humidity Effects on the Thermal Comfort and Heat Balance of the Body

Humidity, one of the most confusing of all climatic parameters in assessing the indoor climate, affects comfort in a number of ways both directly and indirectly, and the avenues by which humidity affects comfort are not completely known. The aim of this study is to comprehend the effects of humidity on thermal interaction between the human body and its environment, and thermal sensation. In this chapter, the effect of humidity on heat and water balance of human body, and in turn on body temperatures and thermal sensation, is investigated. A mathematical model of heat and mass interaction between the human body and the surrounding environment has been established, and the effect of air humidity has been examined under various relative humidity levels by means of using the empirical relations that express thermoregulatory control mechanisms. In the numerical model, human body has been separated into 16 sedentary segments, and possible local discomforts have been taken into consideration. Using the model, changes in the sensible and latent heat losses, body temperatures, skin wettedness, and thermal comfort indices have been calculated and results have been discussed explicitly.

Investigation of the number of particles in an operating room at different ambient temperatures and inlet velocities

ABSTRACT This study presents some field measurements in an operating room of air velocity, ambient temperature and particle counts on the operating table. Moreover, computational fluid Dynamics analyses of the operating room were performed and compared with the measurements. Measurements were taken under the preferred operating conditions by surgical staff (at 19 °C) and then at different ambient temperatures (from 20 to 22 °C,varying by one-degree increments) and average inlet air velocities (Vi) (0.1 and 0.2 m/s). The preferred one by surgical staff is 0.1 m/s and the maximum that can be reached is 0.2 m/s, with the current system. The results show that the particle count decreased at Vi of 0.2 m/s and low temperatures.

Determination of Optimum Insulation Thickness for Different Insulation Applications Considering Condensation

In this study, thermal insulation thickness used in the outer walls of buildings composing of different insulation applications having the same thermal resistance was optimized by considering condensation. The minimum insulation thickness required to prevent condensation (i.e. optimum insulation thickness) in building structural component was determined. Heat and mass transfer calculations within the structural component were performed with respect to various indoor-outdoor temperature and relative humidity values and results were given in graphs. It was observed that optimum insulation thickness is generally increased with an increase in the indoor temperature, indoor relative humidity and outdoor relative humidity. It was concluded that type of insulation application does not significantly affect optimum insulation thickness at low and medium level (θi<0.60) indoor relative humidity conditions. It was also observed that externally insulated wall application generally yields better results at high indoor and outdoor relative humidity conditions.

Three-dimensional air distribution analysis of different outflow typed operating rooms at different inlet velocities and room temperatures

It is important to provide a regular unidirectional air distribution in an operating room to reduce the number of particles. Measurements were taken in the one of the operating rooms at Uludag University Medical School, with laminar air flow unit and two-cornered outlet which was thought to have some airflow problems. Moreover, a three-dimensional computational fluid dynamics model has been developed where the measurements were taken in. The distributions of air velocity, temperature, and relative humidity have been examined and compared with the measurements to validate the computational fluid dynamics analyses. In addition to present model, four-cornered outlet operating room has been analyzed and compared with the results of two-cornered one. It is concluded that the case of four-cornered outlet provides more suitable thermal distribution, which results in a reduction of the particle numbers in the interior. Although there is no significant change in temperature and relative humidity in the operating room, air distribution changes dramatically.