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Khujakulov Saydulla Mirzaevich, Teacher of the department Heat power engineering, Karshi engineering economics institute E-mail: [email protected] Uzakov Gulom Norboevich, Professor of the Department of Heat Power Engineering, Karshi engineering economics institute E-mail: [email protected]
RESEARCH OF THERMO MOISTEN MODE IN UNDERGROUND VEGETABLE STOREHOUSES IN THE CONDITIONS OF HOT - ARID CLIMATE
Abstract: In the article, features of creation optimum thermo Technical mode and results of researches of a temperature field of a soil mass in underground vegetable storehouses are stated.
Keywords: vegetable storehouse, thermo steam, specific thermal emissions, thermo physical measuring.
Transportation of vegetables on the distances measured in tens, and sometimes hundreds of kilometers and this leads to partial loss of a crop and demands the expense of fuel on transportation. Therefore the construction (designing) of small underground vegetable storehouses in places of cultivation of vegetables and on fields of farms, and their optimum power supply is an actual problem.
Long storage of products in underground storehouses in many respects depends from operational and thermo technical characteristics of protections and parameters of internal air and their coordination with
parametres of soil. According to results of J. Fure's researches [1] it is known that special thermal properties of underground constructions - thermo started microclimate - arise because of existence of certain depth in the soil mass which temperature remains approximately a constant even, despite presence of final value of heat conductivity of a layer.
For research of heat moisten mode and measurement ground temperature in underground storehouse we developed thermo physical measuring stand which is presented on (fig. 1)
~ ffi&ä&V^ »ff« 1
Figure 1. The Cross-section underground vegetable storehouse and point of measurement of temperature in ground (1, 2, 3), storehouse (4, 5), embankments of vegetables (6, 7, 8), external air (9) and an internal surface of protection (10). I - a potentiometer, II - the switch; III - thermo steam; IV - the refrigerating chamber; V - soil mass
RESEARCH OF THERMO MOISTEN MODE INUNDERGROUND VEGETABLE STOREHOUSES IN THE CONDITIONS OF HOT — ARID CLIMATE
Typical distribution of temperatures in thickness of a ground for hot environmental conditions of the Kash-kadarya area is presented on (fig. 2). In depending on a season.
Comparison of results of measurements shows that the thermal mode of an underground soil is formed under the influence of two major factors - solar radiation falling on a surface and stream of radio gene heat of terrestrial bowels. Seasonal and daily changes of intensity
of solar radiation and temperature of external air cause fluctuations of temperature of the top layers of earth. Depth of penetration of daily fluctuations of temperature of external air and intensity of falling solar radiation depending on the concrete soil-environmental conditions fluctuates within 15-20 sm to 1.5-2.0 metres. Depth of penetration of seasonal fluctuations of temperature of external air and intensity of solar radiation for conditions of the Kashkadarya area does not exceed than 15-20 m.
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Temperature of the soil, 0C
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Figure 2. The schedule of changing the temperature of a ground depends on depth
Results of measurements shows that in depth h = 3 m in the conditions of Karshi in storage of vegetables (October - March) the average temperature of a ground always positive and stable, and fluctuates in limits t = +2 ^ +7 C. From the point of view of creation of un-
gr r
derground storehouse, this depth is the most suitable as in the plan of thermo starting internal volume of air, and in the plan permanency of this mode. Building of vegetable store house in depth h = 3-4 m gives notably saving of energy for creation of an optimum microclimate.
The special place among underground constructions is occupied with the objects intended for storage of agricultural production. It is known [2; 3] that (in spite of the fact that storehouses concern the category of uninhabited objects) storage production represents object considerable heat - and humid separation.
Problem to complicate that fact that with increase in temperature of storage intensity of the biochemical pro-
cesses proceeding in storing of production increases, and together with them intensity of specific thermal emissions increases. Generalisation of the given various sources [3; 4] shows that the increase in temperature of storage in an arithmetic progression leads to increase of density of thermal emissions in a geometrical progression (fig. 4). Thus, the specific density of thermal emissions q (Vt/kg) with sufficient degree of accuracy is approximated by expression:
q=qo exp (bt) (1)
where q0, b - the constant, accepted on [2].
In usual refrigerating chambers for storage of vegetables the storage mode is characterised by three basic thermo technical n parametres: in temperature, relative humidity and frequency rate of air circulation (speed of air) indoors. Maintenance in chambers of optimum values of temperature, relative humidity and frequency rate of air circulation yields good results. However, in many
cases it is insufficient. It is necessary to provide also optimum (for vegetables of each kind and grade) structure of environment in the chamber, characterizing defined concentration O2, CO2 and N2
Gas exchange of products with environment is characterised by the equalization of breath [4]: C6H12O6+ + 6O2 = 6CO2 + 6H2O + 2824 Kjoule warmth
It is apparently from the results above the balance equalization, breath of products is accompanied by allocation in environment of energy in the form of warmth. Values of these thermal emissions are approximately proportional to intensity of breath of fruits, vegetables and it is defined on the volume of emission of CO2 As a result of breath of fruits and vegetables structure of en-
q, Vt/kg 0,032 0,03 0,028 0,026 0,024 0,022 0,02 0,018 0,016 0,014
0,012' 0,01
vironment in the refrigerating chamber Changes - the oxygen maintenance decreases, and carbonic gas increases. This feature of breath of fruits allows creating in the refrigerating chamber the modified gas environment with the lowered concentration of oxygen 02 and raised carbonic gas C02
Pauperisation (decrease in concentration 02) internal air oxygen and enrichment by its carbonic gas brakes intensity of breath of fruits and vegetables, thereby decreases their losses and increases periods of storage. Thus concentration of oxygen should not be less than 3%, and C02 - more than 10%.
Results of calculations under the formula Gore (1) presented in the form of schedules on (fig. 3).
1 2
3 4 5 6
7 8 9 10 11 t, 0C
0
Figure 3. Intensity of thermal emissions
According to the results of researches it is possible to make the following conclusion that the most suitable criterion defining parametres of a microclimate in underground storehouse, it is necessary to consider seasonal distribution of temperatures in thickness of a
of apples (1), potatoes (2), onions (3) ground and thermo physical properties of the ground. In this plan the most effective thing can be appeared that the underground storehouse intended for storage of fruits and vegetables.
References:
1. Tikhonov A. N., the Samarskiy A. A. Equation of the mathematical physics. - M: the Science, - 1977.
2. OHTn-6-86. All-union norms of technological designing ofbuildings and constructions for storage and processing of a potato and fruit-and-vegetable production. - M: Minplodoovoshkhoz. - 1985.
3. Zhadan. V. Z. Theoretical basis of air conditioning at storage of juicy vegetative raw materials. - M.: Food-processing industry, -1997.
4. Volkind I. L. Technology of storage of potato, vegetables and fruits. - M: Agropromizdat, - 1989.
