Explore chapters and articles related to this topic
Introduction
Published in Laurence J. Street, Introduction to Biomedical Engineering Technology, 2023
When body temperature rises due to increased internal heat production and/or increased ambient temperature or incident infrared radiation, a number of responses can occur. Behaviorally, any organism might seek shade or water, while humans can alter their clothing or simply turn up the air conditioner. Physiologically, blood flow may increase to skin areas where excess heat can be radiated away, and (in humans) sweat glands in the skin produce perspiration, which evaporates and cools the body.
Body Systems: The Basics
Published in Karen L. LaBat, Karen S. Ryan, Human Body, 2019
Muscles play a big role in keeping the body at a healthy temperature. If you exert a great deal of muscular effort working or exercising, you burn large numbers of calories and you feel warm. Excess heat is dissipated when you perspire (sweat) and the perspiration evaporates from the skin’s surface. Wearable products may promote or prevent this natural process. The complexities of thermal balance and thermal comfort are further explored in more detail in many of the body region chapters.
Introduction
Published in Laurence J. Street, Introduction to Biomedical Engineering Technology, 2016
When body temperature rises due to increased internal heat production and/or increased ambient temperature or incident infrared radiation, a number of responses can occur. Behaviorally, any organism might seek shade or water, while humans can alter their clothing or simply turn up the air conditioner. Physiologically, blood flow may increase to skin areas where excess heat can be radiated away, and (in humans) sweat glands in the skin produce perspiration, which evaporates and cools the body.
Review of practices for human thermal comfort in buildings: present and future perspectives
Published in International Journal of Ambient Energy, 2022
Sunil Kumar Sansaniwal, Jyotirmay Mathur, Sanjay Mathur
It is the body heat removal through evaporation of skin perspiration. Some of the body organs (like eyes, lips, etc.) influence less to the heat transfer but it is perceptible. However, the evaporative heat loss at body skin becomes significant due to sweating. The expression used for the calculation of evaporative heat loss is given as follows (Candas 2000): Whereas the evaporative surface area of body () is expressed as follows (Candas 2000): Skin wettedness is a physiological index which can be defined as the ratio of actual sweating rate to that of maximum sweating rate occurred at wet skin. For regulatory sweating, the skin wettedness corresponding to evaporative heat loss is reported to be 0.06. This value becomes unity for skin surface fully wetted with perspiration which is however, impractical and rarely happens. The value of skin wettedness can reduce to 0.02 due to dehydration of outer skin surface longer exposed to low humidity (Lin and Deng 2008). Moreover, the evaporative heat loss is the function of mass transfer coefficient and humidity ratio for the given skin surface temperature (Threlkeld 1970). It represents the combined effect of heat losses due to skin diffusion and regulatory sweating. The expression for evaporative heat loss at body skin is given by (Stoecker and Jones 1988): The relationship between skin wettedness and metabolic rate for equal clothing thermal insulation (0.6 clo) but different vapour resistance is shown in Figure 4.
The effect of environmental variables and metabolic rate on physiological parameters in a hot and humid mine
Published in Science and Technology for the Built Environment, 2022
GuangLei Liu, HeQing Liu, Fen Chen, ShiXian Wu, GuoShan Wu
Miners are engaged in high-intensity work in high-temperature, high-humidity and low-wind-speed environments. The human body continuously releases heat, while the human body gains or loses heat from the environment through convection, radiation and sweat evaporation. However, the physiological functions of the human body require that body temperature be maintained approximately constant to ensure its normal functions. The factors of heat exchange between the human body and the environment include environmental parameters (temperature, humidity, and wind speed), and metabolic rate. The parameters that characterize changes in human physiological functions include skin temperature, core temperature, heart rate, blood pressure, electrocardiogram, body surface impedance. Physiological function adjustment will occur with changes in environmental factors, which will cause fluctuations in human physiological parameters. Changes in physiological parameters can be used as a biological warning signal for studying the human body’s deviation from the “neutral state” in a high-temperature and high-humidity environment. When the air temperature changes, the human body’s thermoregulation system controls the skin temperature through the expansion and contraction of blood vessels to maintain thermal comfort (Wang 1992; Choi and Loftness 2012; Wang et al. 2013; Takada, Matsumoto, and Matsushita 2013; Soebarto, Zhang, and Schiavon 2019). At the same time, when the labor intensity of the human body changes, the heat generated by the human body cannot be dissipated to the environment in time, the body generates heat storage, and the core temperature rises. The human body temperature regulation system is activated to regulate the flow of blood to the skin surface, to regulate the amount of perspiration, and to improve heat dissipation. At present, heart rate (Liu, Lian, and Liu 2008; Choi, Loftness, and Lee 2012), blood pressure (Siqueira et al. 2017), and electrocardiograms (Zhu et al. 2018) have been widely used as predictors of thermal comfort.