known that at low temperatures, in principle, not able to endure
technically significant amount of water. The lower the temperature, the less
water vapor. Dependence of the content of water vapor in the air (absolute humidity
g / kg) on temperature is shown in Figure 1. The graph shows that the cooling
air from 20 to -30 0 C reduces the water vapor content is 70 times. At a temperature
-60 0 C water vapor in the air 35 times less than at -30 0C. In order to understand
how small amounts of water may be in the air at low temperatures
You can say that at t =- 60 0 C, the air contains only one molecule of water
per million air molecules. But this is not the limit at -100 0 C air at 800
once land than -60 0C. It is difficult to even visualize such small concentrations,
and the effect of water impurities on the properties of air do not have to say.
Cryotherapy dry cold air
Cryotherapy dry cold air
Fig. 1 Reduction of water vapor by cooling air.
discussing the presence or absence of cryotherapy with dry cold air
consumer benefits have to decide that the producers cryo-therapeutic group
complexes is meant by the term dry air. In principle there are two possibilities:
Dry air is air with a low content of water or air is passed
special drying.
As figure 1, the cooling of the gas will inevitably accompanied by a decrease
its moisture content.
kritoterapiya and moisture content of air
Fig. 2 Changes in moisture content of air cooling from -120 to-1300S.
Given the differences in the value of the temperature of the gaseous medium supplied to the group
(From -110 to-120 ° C.) and individual car (do not over-130oC), the air group
cryo-therapeutic complex containsmorewater vapor (see Figure 2).
With decreasing temperature, -120 to-1300S moisture content of air decreases
10 times, and the air is cooled to-1500C has a 1000 land than-1200S. Approval
idiosyncratic dry air and the associated consumer benefits
group complexes are groundless.
Maybe in group systems, air ismoredrying? Although
producers do not speak about it, we can estimate in principle the possibility of pre-
drying gas directed into the treatment room. For additional drying gas
flows can offer only one way to absorption of water adsorbent (granular
highly porous materials). However, the adsorptive dehydration is applicable only
When the gas flow has increased pressure (at least 5 MPa). In modern
cryo-therapeutic complexes such conditions are absent. Since the gas circulates
between the cab and a cooling system to compress it would take many times
complicate technology cryostating.
So, getting " dry cold air " is based only
on the freezing of water cooling. And all the arguments about the actual content
Water in group cabins are valid.
A renewed focus on dry air, based on everyday experience,
resulting in contact with low temperatures, the natural level. Indeed,
at temperatures above-200C absolute humidity is high enough,
therefore, the relative humidity of gas (degree of saturation of air with water) is significantly
effect on subjective feelings. In the humid climate of St. Petersburg at
-200C in 1m3 of air will contain 0.9 grams. water (relative humidity
100%). At the same temperature in Yakutsk air can be twice as land
(Relative humidity 50%). Those who have visited these cities in the winter, at
experience examined the ability of water vapor to increase heat loss.
But if the gas has a temperature below-600C, and water vapor in it is so small (0.011
gr./m3) that its heat capacity and thermal conductivity does not depend on the relative
humidity.
But still, there remains one way to transport water in low-temperature gas
flows - migration of crystals of frozen water in the form of frost and snow. The water molecules
during crystallization, form complex spatial stasctures with high
windage. With the rapid decrease in air temperatures, snowflakes are obtained very
small and easily moved through the complex. Maybe in group
booths set up conditions for trapping solid water? To answer this
question we must compare the processes of selection and transfer of frost in the group and individual
complexes.
main source of water in the area of cryo-therapeutic effects
a patient. The water contained in the exhaled air and evaporates from the surface
body. In group complexes of water falls in the volume of the cabin, as the breath, so
and from the surface of the body. In cryo-therapeutic individual cabins patient breathes
atmospheric air, so moisture from the breath of the volume of the cab does not arrive.
Source of water is only skin, and, as shown
Visual observations of the skin, dries up during the first 30 procedures. Estimate the number of
moisture received in the amount of skin is extremely difficult, as conditions for the allocation
sweat at very low temperatures nobody investigated. At the same time, this source
Water is present in both cases, so they can be ignored. Much more
amount of moisture received during breathing patient in the amount of the cab. This source
water is present only in group complexes, and therefore it is necessary to evaluate the ability
cooling equipment to remove frost from the volume of the cab.
compression chiller (see Fig. 3) operates in a closed cycle. Air
out of the cab shown in the heat exchanger - air cooler, where its temperature
reduced by 10-200C. After cooling, the gas returns to the cockpit with the patients.
Cooling leads to the fact that the water is frozen on the surface of the heat exchanger
and the air becomes drier. The process is at a temperature below-1000C, and therefore
the ability of air to carry water in vapor form, is extremely small. For example, in a stream,
withdrawn from the cockpit, (t =-1000C) contained 8.26? 10-3mgr/kg water vapor after
cooled in a heat exchanger to a temperature-1200S, absolute humidity
decreases to 8.13? 10-5mgr/kg. Almost all the water from a stream must remain
in the heat exchanger, but the number of frozen vapor is negligible. Hard water
not hold in the heat exchanger and can return to the cockpit in the air stream.
We compare the amount of water is frozen and exhaled.
From power electric compression chiller (20 kW) and the degree
supercooling the air in a heat exchanger, air flow through the treatment room
amounts to 0.1-0.2 kg / sec. 4 minutes by cab from the procedure, patients will
from 30 to 60 kg of air. Given lagosoderzhaniya air at a temperature of 1000C
(See Figure 1), the flow can make the cabin from the cockpit could make no more
0.5 oz. water.
muchmorewater enters the cabin volume of the breath of patients. Should
Note that for the protection of internal organs from frostbite, patients breathe air
through a cloth filter - a respirator. When you exhale - the fabric becomes a respirator
center of the condensation water from air, with breath - wet tissue warms the air
and cools itself. Filter reduces the mass of the incoming water into the cockpit. 4 minutes
procedure, the patient makes up to 80 breaths, the total volume of 40 liters. Five patients
exhale about 0.2 m3 of moist air, which originally contained up to
400 gr. water.
water vapor in the cabin with cryotherapy
Fig. 3 Distribution of water vapor entered the cabin while breathing patients.
Given the cooling in contact with the material of the respirator, in the amount of cabin air
comes with a temperature of about 50 C. Then will make a 0.2 m3 of air into the cabin to
10 grams of water vapor. Cabin volume of 8 m3 may be in the form of a pair of nomorethan
0.0015 mg of water, so the pair immediately turn into a small snowflakes (ice fog).
Streams makes for the procedure only 0.5 oz. water, therefore,
9.5 oz. remain in the cockpit. Obviously, the design group complexes are not
ensures the removal of water received from the patient's breathing. From one procedure to
number of frost in the cockpit and communications shall increase, to remove water
condensate after the end of the complex, it is necessary to carry out actions
to clean up the complex from the solid water. And indeed, in the technological cycle
complex includes defrost mode, duration 2-3 hours, which
lets get rid of accumulated water.
Individual complexes with nitrogen-cooled (see Fig. 3) are working on an open
cycle, as part of the gas passing through the treatment room to play in the atmosphere.
Number of removed gas is determined by the flow of liquid nitrogen cooling system
and is 1,5 - 2 kg / min. The circulation flow through the cabin is 0,1
- 0,2 kg / s (60 - 120 kg / min). Altogether during the procedure (3 minutes) through the cabin
goes up to 350 kg of coolant. Powerful gas flows create conditions for
Transfer of frost formed on evaporation of perspiration into the atmosphere (10%) and the block
cooling (90%). Terms of nitrogen cooling are such that in the contact heat exchanger
Snowflakes intensively irrigated with liquid nitrogen. When wetted by liquid nitrogen windage
frost decreases. A mixture of liquid nitrogen, and the frost settles in the inner cavities of the cooler.
Moisture received since the patient's skin, quickly removed beyond the procedural
cab. Visually, it is clear that within 30-40 seconds after the commencement of the glacial
mist disappears, and the cabin visible to the bottom. Ability to evacuate
water is so high that patients can go into the cockpit after the pool,
wet skin. All the same, 40 to the skin dries out and the gas in the cabin is cleaned
from the icy mist.
analysis shows that all the determining moisture content of gas
parameters in the cryotherapy group of considerably less individual
complexes with nitrogen cooling.
Consumers cryogenic physiotherapy equipment can easily estimate
the degree of dryness of the air in the cabin. If some time after the commencement of the
fog disappears, cooling equipment to cope with the removal of moisture. If
ice fog kept constant, all the talk about pre-air drying
devoid of any physical meaning.
In conclusion a few words about local cryotherapy with dry air at-300C.
Firstly, at such a high temperature gas to get cryotherapeutic effect
simply impossible. Temperature level-300S typical winter climate of many
Russian regions, but cases of diseases in natural air baths
temperature of-300C or who have not been described. If the gas temperature above-1300S procedure
in principle does not cryotherapeutic effect. But the humidity at
temperature of-300C is high enough, as the air is dried by
freezing water in cooling and relative humidity to 100%. So
, neither cryotherapy nor dry air in the apparatus with a temperature of-300C
just do not.