مقالات رزومه مهدی افضلیان

The present study aimed to investigate the effects of air inlet location and flow characteristics on the performance of a personalized ventilation system. For this purpose, a near-body personalized ventilation system is numerically simulated in an office room with the presence of a thermal manikin. Three air inlet arrangements (in front of the feet, in front of the abdomen, in front of the face) were modeled, two air temperatures (16 and 20℃) and two air velocities (1 and 2m/s) were assigned to each arrangement. Finally, airflow temperature distribution, velocity distribution, and the overall and local temperature and thermal sensation of different body segments are determined. In some cases, by changing the air inlet placement from the front of the feet to the abdomen and head, the whole-body thermal sensation is cooled by 0.54 and 0.6 units, respectively. In all cases, hands and head felt cooler than the wholebody thermal sensation, which shows that the bareness of a segment has a significant effect on its feeling in personalized ventilation systems. Unlike the foot, the head is an effective local segment for non-uniform cooling purposes in warm conditions, and due to its effect on the whole-body thermal sensation, cooling the head would be an effective way to reduce energy consumption.

Thermoregulatory models based on thermoreceptors have attracted the attention of researchers in recent years due to their conformity with the basis of human thermal perception. For this reason, various models have been presented such as STB, ITB, MSTB and JOSTB. In the present study and in continuation of previous studies, an individual multi-segment thermoregulatory bioheat (IMTB) model has been introduced which can evaluate the temperature of various segments of the body by considering the effects of individual parameters such as height, weight, age and gender. In this study, the body is subdivided into 17 segments, 3 layers and the blood circulatory system consists of arteries, veins and superficial veins. Also, the effects of individual parameters on physiological parameters, thermoregulatory mechanisms and heat transfer of the body have been investigated. Finally, the performance of the new model in predicting local and mean skin temperature was validated against different experimental data. The results indicate that by considering the individual parameters, the new model can precisely predict the local skin temperature with mean absolute error of 0.4℃.

Modeling body’s circulatory system with many vessels and capillaries and its effects on the body thermal conditions is complex. many thermoregulatory models have tried to model the effect of the circulatory system with simplistic and inaccurate assumptions. The MSTB model considers the blood as a node with specific heat capacity and constant temperature depends on the overall body thermal conditions. This assumption can lead to significant errors in estimating the some organs temperature. Therefore, a JOSTB model has been introduced by the approach of modifying the blood circulatory system. In this model, the body is divided into 17 segments and 3 layers and blood flow in the organs with arteries in the core of each segment is considered. The heat and mass transfer and the localized Pennes equations in different segments have been used to determine tissue temperature. Comparing JOSTB results with MSTB and experimental results show that JOSTB accurately predicts the body temperature. The average errors for the local skin temperature in the wide range of operative temperatures (10-50 ) are equal to 2.3  and 1.1   for MSTB and JOSTB.