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Numerical investigation on the heat flux properties of a thermal manikin in slee** environments applying task/ambient air conditioning

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Abstract

As an energy-saving equipment, task/ambient air conditioning (TAC) system was widely used in slee** environment in recent years. The TAC can deliver cooling air directly to the slee** person, resulting that the micro climate around the human body becomes very critical in the evaluation of human beings’ thermal comfort. Different from sitting and standing, slee** human body is always at lying posture, and thus at a lower metabolic rate than at waking status. To understand the heat balance between a slee** body and the surrounding environment, investigation on the heat loss of human body becomes necessary. Hence, a numerical study on the body heat loss characteristics of a thermal manikin at slee** state in a bedroom utilizing a TAC system was carried out. The convective heat transfer, radiative heat transfer, evaporative heat loss from skin and respiratory heat loss and their ratios were quantitatively analyzed. The results indicate that the convective heat transfer took the first place, accounting for about 80% of the total heat loss, and Latent heat loss accounted for 15.9%–21% of the total heat loss. In addition, the heat loss at different supply conditions was numerically studied. Results showed that the supply air temperature, flowrate and humidity play different effects on body heat loss. Contributions of this study are meaningful for the accurate control of micro climate of human activities.

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Abbreviations

A D :

Dubois surface area (m2)

C :

Convective heat loss (W m−2)

C p,a :

Specific heat of air (J kg−1 K−1)

C res :

Respiratory heat loss (Sensible) (W m−2)

E res :

Respiratory heat loss (Latent) (W m−2)

E sk :

Evaporative heat loss from skin (W m−2)

f cl :

Clothing area factor

G ω :

Generation of ω

\(\tilde{G}_{\text{k}}\) :

Generation of turbulence kinetic energy due to mean velocity gradients

h′ :

Overall sensible heat transfer coefficient (W m−2 K−1)

h conv :

Convective heat transfer coefficient (W m−2 K−1)

h e :

Evaporative heat transfer coefficient (W m−2 K−1)

I a :

Thermal insulation (clo)

i m :

Total vapor permeation efficiency

k :

Turbulent kinetic energy (J kg−1)

K res :

Proportionality constant

L R :

Lewis ratio (K kPa−1)

M :

Metabolic heat production (W m−2)

\(\dot{m}_{\text{res}}\) :

Pulmonary ventilation rate (kg s−1)

P a :

Water vapor pressure in ambient air (kPa)

P sk,s :

Water vapor pressure in saturated air at tsk (kPa)

P t :

Ambient pressure (kPa)

Q latent :

Latent heat loss from thermal manikin (W m−2)

Q r :

Radiative heat loss (W m−2)

Q res :

Respiratory heat loss (W m−2)

Q s :

Supply air flow rate (L s−1)

Q total :

Total heat loss from thermal manikin (W m−2)

R :

Radiative heat loss (W m−2)

R e,cl :

Evaporative heat transfer resistance of clothing layer (W m−2)

R e,t :

Total evaporative resistance (W m−2)

R t :

Total equivalent thermal resistance between body and surrounding environment (including clothing and boundary resistance) (m2 K W−1)

RHa :

Relative humidity in ambient air (%)

RHs :

Relative humidity in supply air (%)

S k :

User defined source term

S ω :

User defined source term

t :

Air temperature at a measurement position (ºC)

t a :

Ambient air temperature (ºC)

t ex :

Exhaled temperature (ºC)

T s :

Supply air temperature (ºC)

t sk :

Average skin temperature (ºC)

t uz :

Average air temperature in an unoccupied zone (ºC)

u :

Air velocity (m s−1)

v a :

Air velocity in the ambient environment (m s−1)

W :

Workload (W m−2)

w :

Skin wetness

W a :

Humidity ratio of inspired air (ambient air) (kg kg−1)

W ex :

Humidity ratio of exhaled air (kg kg−1)

Yk :

Dissipation of k

Y ω :

Dissipation of ω

ρ :

Density (kg m−3)

ω :

Specific dissipation rate (s−1)

Γ k :

Effective diffusivity of k (m2 s−1)

Γ ω :

Effective diffusivity of ω (m2 s−1)

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Funding

The study was supported by Shandong Provincial Natural Science Foundation, China (No.: ZR201910240273), the Fundamental Research Funds for the Central Universities (No.: 18CX02077A), Research Foundation for Talents of China University of Petroleum (East China) (No.: YJ201501018).

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Authors and Affiliations

  1. Department of Gas Engineering, College of Pipeline and Civil Engineering, China University of Petroleum (East China), Qingdao, Shandong, China

    Ning Mao

  2. School of Mechanical Engineering, Bei**g Institute of Technology, Bei**g, China

    Mengjie Song

  3. Institute of Process Equipment and Control Engineering, Zhejiang University of Technology, Hangzhou, 310014, China

    Yingjie Xu

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  1. Ning Mao
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Correspondence to Mengjie Song.

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Mao, N., Song, M. & Xu, Y. Numerical investigation on the heat flux properties of a thermal manikin in slee** environments applying task/ambient air conditioning. J Therm Anal Calorim 147, 1675–1688 (2022). https://doi.org/10.1007/s10973-020-10515-2

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  • DOI: https://doi.org/10.1007/s10973-020-10515-2

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