Experimental proof of numerical prediction

17.5.2 Experimental proof of numerical prediction

The numerical prediction and the jacket designed on basis of numerical sim- ulations was proved in various tests. The first series of 48 measurements was carried out in a thermal chamber. The measurements were performed with healthy candidates at the age between 30 and 45 years, P D 168 188

181

F igure 17.4: Overheating protection jacket designed on the base of simula- tions.

Figure 17.5: Temperature distributions around the body with continuous ice distribution and with ice briquettes. Results of numerical simulations after

60 minutes.

182

Figure 17.6: Development of the averaged temperature in the air gap between the underwear and the ice protection on the human chest. Comparison be- tween the measurement (solid line) and the numerical simulations (dotted line).

183 Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more 183 Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more Click on the ad to read more

from the empirical formula A D 0:24m 0:4 P [41]. The candidates weared the jackets (see Fig. 17.4)were doing the work at a rate of about M D 420

watts which corresponds to a hard work typical for the mining industry. The

0 . The temperature has been measured in the air gap between the underwear and the ice at seven

points around the chest (section 2 in Fig. 17.1). The temperature averaged over these points is presented in Fig. 17.6. The discrepancy between the measurement and the numerical simulations does not exceed 14 percent af- ter 60 minutes of the real time. This agreement can be considered as quite satisfactory taking the simplicity of the used model and complexity of the problem into account.

Figure 17.7: Test person weared overheating protection jacket (left) and distribution of the temperature sensors on the human body (right).

The task of this study is the determination of the temperature in the body core. It is a difficult problem since the direct measurement is impossible. The experience gathered in physiology [42] shows that the core temperature can reliably be determined if the temperature T j at five characteristic points (forehead, chest, hand, thigh and shin) is known (see Fig.17.7). The sensors were mounted directly on the human skin with the rate of press not exceeding 0:2 0:25

Pa. The accuracy of measurements is estimated as 0:1 0 C . These temperatures are summed up with weighting coefficients w j . Each tempera-

ture is nearly constant within a certain area A j . The weighting coefficients are calculated as the ratio of A j to the total body surface A, i.e. w j DA j =S . The averaged temperature is calculated then from the formula [41]

T D 0:07T 1 C 0:5T 2 C 0:05T 3 C 0:18T 4 C 0:2T 5 (17.11)

(17.12) The correlation factor K is taken from the table 17.5 [39]. Figure 17.8 shows

T i nne r D KT r ect al C .1 K/T

the time history of the inner temperature T i nner . The most important con- clusion drawn from this figure is that the inner temperature T i nne r doesn’t exceed the threshold 36 0 within 60 minutes. Thus, the aim of the design has been achieved.

Table 17.5: Coefficient K depending on the test person feelings and energy

2 expenditure E D M=A .W=m 2 / . A is the body surface (m ) and M is the work (W )

feeling j E

slightly chilly

slightly warm 0.70 0.70 0.70 0.70 0.70

The second series of measurements was carried out directly during the work in a cole mine at the temperature not higher than 60 0 without fire action.

During one year of observations no equipment fault has been documented. The temperature of workers was kept at a prescribed level during at least

55 60 minutes as predicted both in numerical simulations and thermal chamber tests.