RU2052740C1 - Method and system for thermostatic storage of products - Google Patents

Abstract

FIELD: refrigerating engineering. SUBSTANCE: reservation in form of lithospherical block is made in cold period in layer of soil close to its isothermal boundary with cold accumulator located in this layer. Atmospheric air is positively blown through cold accumulator. Cooling section of cooling agent of closed circulating loop is located in ice and soil block. EFFECT: enhanced efficiency. 6 cl, 1 dwg

Description

 The invention relates to methods and systems for thermostatic storage of products in a refrigerated form and can be used for long-term storage of agricultural products, in particular in vegetable stores close to the place of harvesting.

A known method of storing products in chambers, the cavity of which is filled with circulating refrigerant. In the heat-insulating ceiling, made in the form of a duct, there are ventilation openings that are open in cold time for the cavity to communicate with the external environment. As a result, the upper refrigerant layer is supercooled, creating a natural reserve of cold energy in the form of ice over the upper enclosure of the working volume of the chamber. During the warm season, the ventilation openings are constantly closed. In this way, a stable temperature can be maintained for a certain time in the working volume of the chamber. If necessary, in the warm period, the supply of natural energy of the cold can be increased by refueling a piece of ice, for example, from a riot [1]
The above method and device provide due to the limited supply of cold, imperfections in the communication system of the refrigerant with cold atmospheric air, very short terms and volumes of thermostatic storage of products.

 To a certain extent, these drawbacks have been eliminated in the method of storage of products, according to which, in the cold season, the cold storage device is charged with an intermediate coolant. The device for accumulating cold is made in the form of a vertical column, the upper part of which is located above the soil surface and is designed to cool the intermediate coolant in the cold period. The vertical column includes the cooling section of a closed circulation circuit designed to supply refrigerant through the second section of the specified circuit to the storage radiators (ed. USSR certificate N 1153208, class F 25 D 1/00, 1982).

 The presence of the upper part of the vertical column located above the soil surface during the warm period leads to heating of the intermediate heat carrier, and, consequently, the refrigerant, as a result of which the cooling capacity decreases and the storage time of the products is limited.

 The need to deepen the soil of a sealed column with an intermediate coolant and the included communications of a closed refrigerant circulation circuit complicate the design and reduce the reliability of the system for implementing the described method.

 The aim of the invention is the creation of such a method and system of thermostatic storage of products, mainly vegetables and potatoes, in climatic zones with an average positive annual temperature and seasonally changing external heat transfer conditions, i.e. where warm summers give way to cold winters, which would ensure, with the simplicity and reliability of technological equipment, low energy consumption, storage duration with minimal losses.

 The goal is achieved by the fact that in the soil layer close to its isothermal border, in the cold period, using a ground moisture, form a cold reserve in the form of an ice-ground array, placing a device for accumulating cold in this layer through which atmospheric air is forced to blow, while the cooling section the refrigerant of the closed circulation circuit is located in an ice-ground mass. It is advisable to add moisture to the soil layer close to its isothermal boundary.

 In the system for implementing the method of thermostatic storage of products, the device for accumulating cold can be made in the form of a multisection pipeline equipped with heat-conducting sections in contact with the ice-ground array, and the refrigerant cooling section of the closed circulation circuit is also equipped with heat-conducting sections located in the ice-ground array between the pipe sections of the device for accumulation of cold.

 It is advisable to install a filter-moisture separator at the entrance to the pipeline of the device for accumulating cold, and apply a coating of non-wettable material to the internal surfaces of this pipeline.

 The system can be additionally equipped with tanks located above the soil surface and designed to collect precipitation, as well as pipes connected to containers to supply atmospheric moisture to the soil layer close to its isothermal boundary.

 The drawing shows a thermostatic storage system of products.

 According to the proposed method, in a specially prepared or natural foundation pit, at a depth close to the isothermal boundary of the area in which the storage is located, a multi-section pipeline, cold storage devices and a refrigerant cooling section of a closed circulation circuit are installed, the radiators of which are installed in the storage. The foundation pit with the communications located in it is covered with soil.

 In the cold period, by forced blowing of the cooled atmospheric air through a pipeline in the zone of its location, a cold reserve is formed using ground moisture in the form of an ice-ground array, in which there is a section for cooling the refrigerant supplied to the storage radiators.

When storing vegetables or potatoes at a temperature of 0 ° ^C mass of 1 m according to the Research Institute breeding and seed vegetables per day heat flow of about 800 kcal.

The heat balance equation for the proposed storage method is written as:
Q _o Q _gr + Q _l + Q _c , where Q is _the amount of heat generated by one ton of vegetables per day;
Q _{gr the} amount of heat transferred to dry soil, determined by the expression
Q _gr m $\genfrac{}{}{0ex}{}{\text{.}}{\text{gr}}$ With _{river gr} (t _o t _beg) ; Q _{l the} amount of heat transferred to water when it turns into ice, defined by the expression
Q _l m $\genfrac{}{}{0ex}{}{\text{.}}{\text{l}}$ With _{R. l} (t _about t _beg );
Q _{c the} amount of heat released during melting ice;
m _gr dry ground mass;
With _r.gr heat capacity of dry soil;
m _l ice mass;
With _{r.l the} heat capacity of ice;
t _o ice melting temperature;
t _nach initial temperature of the frozen soil.

, где G масса хранимых овощей в тоннах;
τ время, в течение которого производят хранение, в тоннах;
α количество воды, находящейся в грунте (влажность) в
λ_л скрытая теплота фазового превращения льда ( λ_л 79,77 ккал/кг).The required mass of the ice-ground array for storing vegetables in the specified conditions is determined from the expression
M _gr =

where G is the mass of stored vegetables in tons;
τ is the time during which storage is carried out, in tons;
α the amount of water in the ground (humidity) in
λ _{l is the} latent heat of the phase transformation of ice (λ _l 79.77 kcal / kg).

1040 т
Этот расчет показывает, что в принятых условиях хранения, на каждую тонну сохраняемой продукции достаточно иметь одну тонну резервата в виде льдогрунтового массива. При изменении условий, например, увеличении вдвое влажности естественным путем или введении дополнительной влаги, собираемой и вводимой специально, то соответственно вдвое можно сократить массу и объем льдогрунтового массива, либо продлить время хранения в теплый период.Below is a demonstration calculation ldogruntovogo array weight α humidity of 30% and an initial temperature t _nach 15 ^C. Storage 1000 t vegetables for 60 days
M _gr =

1040 t
This calculation shows that under the accepted storage conditions, for each ton of stored products, it is enough to have one ton of reserve in the form of an ice-ground array. If the conditions change, for example, by doubling the moisture in the natural way or by introducing additional moisture that is specially collected and introduced, then the mass and volume of the ice-ground mass can be reduced by half, or the storage time can be extended in the warm period.

Based on the foregoing, we can conclude that the proposed method can be carried out in climatic zones with an average positive annual temperature and seasonally changing external conditions (cold winters and warm summers) using the above calculations, as well as thermodynamic calculations to determine the required amount of forced flow through the pipeline during the cold period of atmospheric air. According to the thermodynamic calculation, for the formation of the mass calculated above for the mass of the ice-ground mass, it is sufficient to blow out the cooled atmospheric air with a flow rate of 6 m ³ / s for 40-45 days at t ^о С 15 ^о . Naturally, specific weather conditions administered adjustments to the calculated parameters, as a practical southern limit of the workpiece and storing natural ice is line Kishinev Terrible Frunze partially tending to January isotherm 3 ° ^C, which is the conventional temperature limit between moderately warm and moderately cold climates, there is every reason to believe that the proposed method is effective north of the specified temperature boundary.

 Isothermal (practical independence from atmospheric temperature fluctuations) soil depth is 10-20 m at the southern limit. This depth decreases north of the named limit.

≈ 19, где h_г, h_c глубины грунта, на которые проникают годовые и суточные колебания температуры;
τ_г τ_c соответствующие периоды времени (365 сут и 1 сут), определяем, что глубина постоянной температуры для торфа составляет 4,75 м, а для песчаного грунта 19 м.Based on the fact that the daily temperature fluctuations penetrate into the peat layer at a depth of 0.25 m, and into the sand layer at 1 m from the expression:

≈ 19, where h _g , h _{c are} the soil depths that penetrate annual and daily temperature fluctuations;
τ _g τ _{c the} corresponding time periods (365 days and 1 day), we determine that the constant temperature depth for peat is 4.75 m, and for sandy soil 19 m.

, где R удельное радиационное охлаждение (отрицательный радиационный баланс) за год;
t средняя температура атмосферы;
с и λ удельные тепло- и теплопроводность замороженного грунта;
τ время;
A_c средняя для замерзшего слоя грунта годовая амплитуда;
r удельная теплота льдообразования в грунте.In practice, however, many factors influence the location of the zone of constant soil temperature, in particular, the depth of winter freezing of the soil. In the simplest particular case, when it is assumed for the middle latitudes of the country that in the cold season the turbulent heat exchange with the atmosphere is approximately compensated by reverse radiation, is:
h

where R is the specific radiation cooling (negative radiation balance) for the year;
t is the average temperature of the atmosphere;
c and λ specific heat and thermal conductivity of frozen soil;
τ time;
A _c average annual amplitude for the frozen soil layer;
r specific heat of ice formation in the soil.

 The effectiveness of winter cold recharging of the soil depends on the climate, the conditions of cold recharging, and the thermophysical characteristics of the soil, however, for sure, it can be noted that in the middle zone, for example, the Moscow region, the application of the proposed method is effective in comparison with traditional refrigeration plants operating on liquid nitrogen, Freone, etc. The cost of one cubic meter of frozen soil using liquid nitrogen is several times (up to 10) higher than the cost of one cubic meter of soil obtained according to the proposal Agile method.

 The system for implementing the method of thermostatic storage of products contains a vegetable store 1 of the product, a device for accumulating cold in the cold period in the ice-ground mass 2, which is a reserve of cold accumulated in cold time and spent in warm time. The ice-ground mass is located in a soil layer, preferably hygroscopic, for example, based on peat, at a depth close to its isothermal boundary, of the order of 2-10 m.

 The device for accumulating cold includes an intake-ventilation unit 3, a filter-moisture separator 4, a multi-section pipe 5 with heat-conducting sections 6 in contact with the ice-ground array, and a chimney 7 installed at the outlet of the pipe 5.

 The system is also equipped with a closed refrigerant circulation circuit 8 with a pump (not shown in the drawing), radiators 9 installed in the storage, and a refrigerant cooling section 10 included in the ice-ground array. On the site 10 there are heat-conducting sections 11 located between the heat-conducting sections 6 of the pipeline 5.

 To operate in stand-alone automatic mode, a control unit (BU) 12 is provided that controls the on-off of the intake-ventilation unit 3, the refrigerant pump for pumping the refrigerant of the closed circulation circuit 8 and the shut-off and control equipment 13 of the said circuit and the device for accumulating cold. This unit has sensors located in the required places.

 To prevent freezing of atmospheric moisture to the inner walls of the pipeline 5, a coating of non-wettable material can be applied to them.

 To collect and supply additional moisture to the ice-ground massif, a forced water supply pipeline can be connected to it or, as shown in the drawing, the system can be equipped with tanks 14 designed to collect precipitation and connected to them by pipes 15 for supplying atmospheric moisture to the layer close to its isothermal boundary.

 The system for implementing the method of thermostatic storage of products operates as follows.

 Vegetables or potatoes, peeled and dried accordingly, are placed in a storage 1 equipped with a ventilation system. With the onset of the cold period, through the intake-ventilation unit 3, atmospheric cooled air in a low-compressed mode with a second flow rate of several cubic meters per second is pumped through an open pipeline 5, which, together with the sections 6 mounted on it, removes heat from the adjacent soil containing moisture, turning it into ice and cooling the ground. The exhaust air is removed through the exhaust pipe 7. Over time, as the cold air is blown through the pipe 5, the adjoining mass of soil saturated with moisture grows in volume, forming a predetermined ice-ground array 2, which serves as a cold reserve.

 Storage 1 is a thermoconstant room, where in the cold period of time traditional air heating is performed within the specified limits, and in warm time it is cooled using the described system. Management of these processes is automated and is performed from block 12 both within one day and throughout the storage season. Block 12, on the command of the sensors, controls the shut-off and control equipment 13, for example, turning off the intake-ventilation unit 3, shutting off the pipeline 5 and turning on the closed refrigerant circulation circuit 8 during winter thaws and in the warm period (spring, summer). When circuit 8 is turned on, its section 10 transfers the cooled refrigerant to the radiators 9 of storage 1. The largest refrigerant consumption occurs naturally in the warm season, when the closed circulation circuit 8 works almost continuously, using the cold stored in the reserve of the ice-ground mass. Moreover, since the reserve is located in a soil layer close to its isothermal boundary, most of the stored cold is spent on maintaining the set temperature in the storage.

 As already mentioned above, the composition of the soil, its physical and mechanical properties, high humidity, thermal insulation of the massif and other qualities contribute to the duration of preservation of the reserve.

 To accumulate moisture in the soil, an artificial water supply to it or the accumulation of atmospheric, soil moisture in the period preceding the cold season can be used. For this, atmospheric moisture storage devices of various designs can be used, for example, containers 14 with nozzles 15 entering the soil.

 Such a system of thermostatic storage of products (vegetables, potatoes) provides low energy costs with the simplicity and reliability of technological equipment.

Claims (6)

 1. The method of thermostatic storage of products in climatic zones with an average positive annual temperature and seasonally changing external heat transfer conditions by supplying atmospheric air in the cold season to recharge the cold accumulator located in the ground and pumping refrigerant through a closed cavity located in a closed circulation circuit storage, characterized the fact that atmospheric air is supplied in a soil layer close to its thermal boundary, with the formation of a cold reserve in the form of of the atmospheric ice-ground mass using ground moisture, and through the latter, atmospheric air is forcibly continued to be supplied, and cooling of the refrigerant before pumping to the storage is carried out in the ice-ground mass.  2. The method according to claim 1, characterized in that the moisture layer is additionally supplied to the soil layer close to its isothermal boundary.  3. The system of thermostatic storage of products containing a device for accumulating cold and a closed circulation circuit with a refrigerant cooling section, characterized in that the device for accumulating cold is made in the form of a multi-section pipe equipped with heat-conducting sections in contact with the ice-ground array, and the refrigerant cooling section is additionally equipped their heat-conducting sections located in the ice-ground mass between the sections of the pipeline device.  4. The system according to claim 3, characterized in that a filter-moisture separator is installed at the inlet of the device’s pipeline.  5. The system according to PP.3 and 4, characterized in that on the inner surface of the pipeline of the device is coated with a non-wettable material.  6. The system according to claims 3 to 5, characterized in that it is equipped with containers for collecting atmospheric precipitation located above the soil surface, as well as pipes connected to containers for supplying atmospheric moisture to the soil layer close to its isothermal boundary.

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