**8. Algorithm for changing the cooling gas temperature during the individual and group WBC procedures**

compression cooling systems on gas mixtures [7]. To lower the temperature, it is necessary to use other heat transformation cycles in the cooling system, the power of which will allow compensating for the heat load associated with WBC

*Algorithm for changing the temperature of the of the cooling gas with the technology GWBS and IWBS.*

When designing cooling systems of the WBC zone, it is necessary to adequately estimate the power of the heat fluxes that need to be compensated. It was shown above that during the WBC procedure, 440 kJ/m<sup>2</sup> of the heat is released from the patient's body surface, and the mean heat flux from the body to the cryogenic heat carrier varies from 3.5 to 2.3 kW/m<sup>2</sup> (**Table 2**). Taking into account the surface area of the body (1.6 m<sup>2</sup> [7]), the heat input from one patient will be 700 kJ; the mean power of the heat input is 4.6 kW. It is necessary to spend at least 2.7 kg of liquid nitrogen only to remove the heat released from a patient's body surface with a gas

*rLN* þ *cLN Tg* � *T*″

where *rLN* means the heat of vaporization of nitrogen, *rLN* = 199 kJ/kg;*сLN* means

Estimated nitrogen flowrate for removal of the heat from the body surface is 2.7 times higher than in modern nitrogen-cooled WBC installations [13]. To restore the WBC effectiveness, it is necessary to provide cryotherapy installations with suffi-

The heat input from the patients *Q HC* is only the useful part of the heat load on the cooling system. In addition, it is necessary to compensate for the heat input from the walls of the thermal fencing of the WBC zone and *QTI* the heat that the warm gas fluxes bring from the adjacent volumes (lock chamber or environment) to the volume of the treatment cab *QGC*. The total heat load is defined as the sum of

*LN* <sup>0</sup> (25)

*LN* = 78 K.

*LN* means the boiling

**9. The heat load on the cooling system of the WBC zone**

*Technique and Technology of Whole-Body Cryotherapy (WBC)*

*DOI: http://dx.doi.org/10.5772/intechopen.83680*

*GLN* <sup>¼</sup> *QHC*

the heat capacity of nitrogen vapor, *cLN* = 1.002 kJ/kg; and *T*″

point of liquid nitrogen at atmospheric pressure,*T*″

procedures.

**Figure 11.**

with the temperature of *Tg* = 140 K:

ciently powerful cooling systems.

heat received from different sources:

**149**

Installations for GWBC consist of two or three heat-insulated rooms with different air temperatures [7]. Patients pass from the treatment room to the chamber with the minimum temperature (main chamber, MC) and back through the lock chambers (LC). In most modern installations, the temperature in the main chamber is maintained at 160 K and in the lock chamber means at 210 K. At the time of entry (exit) of patients into the LC or MC, warmer air enters from adjacent volumes. Because of this, the air temperature in the MC volume increases by at least 25 K. From the body surface of each patient, 3.5 to 4.5 kW of heat is released into the MC volume. Taking into account these factors, the actual GWBC temperature regime depends not only on the choice of the nominal temperatures in MC and LC but also on the power of the cooling system. Another uncertainty factor is the duration of stay of patients in the main cab. There are different opinions about the advisability of pre-cooling the body surface at an intermediate temperature of 210 K. Some researchers believe that a gradual decrease in temperature increases subjective comfort and safety [7]. In other works it is proposed to reduce the time of stay of patients in LC to a minimum [13]. Given all the reasons presented, it is obvious that it is extremely difficult to simulate the GWBC process. The temperature of the cooling gas varies according to a complex schedule, which consists of at least eight stages (**Figure 11**).

The algorithm of changing the gas temperature in IWBC is much simpler (**Figure 11**). The patient enters the cab filled with atmospheric air, which is quickly replaced by vapors of liquid nitrogen with a temperature not higher than 140 K. The time to reduce the gas temperature in the IWBC cab to the optimum level depends on the power of the cooling system and is at least 20 sec.

Taking into account the results of simulating the WBC process under conditions of a constant gas temperature, it can be argued that the GWBC procedures using the algorithm shown in **Figure 11** do not provide significant therapeutic outcomes. To restore the effectiveness of GWBC, it is necessary to significantly reduce the minimum air temperature in the main treatment cab. Experiments on a mathematical model of the body shell showed that the effectiveness of GWBC reaches the optimal level when the air temperature in the main cab drops to 130 K. However, modern installations for GWBC cannot maintain the temperature at this level, since they use *Technique and Technology of Whole-Body Cryotherapy (WBC) DOI: http://dx.doi.org/10.5772/intechopen.83680*

**Figure 11.** *Algorithm for changing the temperature of the of the cooling gas with the technology GWBS and IWBS.*

compression cooling systems on gas mixtures [7]. To lower the temperature, it is necessary to use other heat transformation cycles in the cooling system, the power of which will allow compensating for the heat load associated with WBC procedures.
