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20за б№шою шльшстю показнишв були отримаш для нелшшно! регресшно! моделi, побудовано! на ос-hobí чотиривимiрного перетворення Джонсона для амейства SB. В подальшому для побудови нелшш-но! регресшно! моделi для оцiнювання розмiру PHP-застосункiв з вiдкритим кодом плануеться ви-користати додатковi набори даних.
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RESEARCH OF THE OPERATION MODES AND RETROFIT OPTIONS OF THE BEVERAGE
COOLER REFRIGERATION SYSTEM
Khmelniuk M.
Dr of Sci., Professor Odessa National Academy of Food Technologies, Kanatna str. 112, Odessa, Ukraine Konstantinov I. Graduate student Odessa National Academy of Food Technologies, Kanatna str. 112, Odessa, Ukraine Ostapenko O. Ph.D., Associate Professor Odessa National Academy of Food Technologies, Kanatna str. 112, Odessa, Ukraine Talibli R.
Graduate student Odessa National Academy of Food Technologies, Kanatna str. 112, Odessa, Ukraine
Abstract
The analysis of the design and operation of the ON-90 beverage cooler is carried out. The refrigeration system is designed and the design flaws are revealed. Changes have been made and the problem of condensate formation has been solved. The change in the location of the thermostat is substantiated. An experimental experiment was
conducted, and the choice of heat exchanger was substantiated. A control check of the work was carried out and a technical map was created. The operation of the system on R404a and R290 is investigated.
Keywords: Refrigeration equipment; Temperature; Energy consumption; Beverage cooler; Heat exchanger; R404; R290.
Commercial refrigeration equipment is an integral part of the modern society. After all, most foods require compliance with storage rules to maintain the appearance and quality. But as consumer needs increase, cold is also used to improve food consumption and ease of sale. One of these units is a beverage cooler designed for instant cooling and bottling of the beverages, and their consumption directly at the point of sale. Many companies that manufacture commercial refrigeration equipment, do not miss this type of product [2, 3]. A 3D model of a water cooler was created and the concept of construction based on ON-90 was considered (Fig. 1).
The basic principle of operation of the ON-90 beverage cooler is to accumulate cold by freezing the ice field around the evaporator. When choosing the equipment, the length of the evaporator tube was selected ac-
cording to the heat capacity of the water volume (coolant) in the tank equal to 30 dm3. In addition, it is taken into account that the weight of the ice field should be 60-70% of the volume of the coolant, ie about 17 kg, selected dimensions of the evaporator tube. The evaporator is made in the form of a spiral. The refrigeration system is completed with the Embraco Aspera EMT6165GK compressor. Installed service-free condenser LU-VE STFT 14221 with technical characteristics: 1000Wt at AT = 15K. The selection of the throttle device (capillary tube) was performed in DanCapTM software from Danfoss. After installing and connecting the refrigeration system, the beverage cooler is switched on and checked for the first time. According to the requirements of beer manufacturing company, the time spent on freezing the ice field should be about 5 hours [7, 8].
Fig. 1. Beverage cooler model ON-90 1) compressor; 2) compressor support; 3) thermostat; 4) power indicator; 5) condenser; 6) housing; 7) coolant tank; 8) evaporator; 9) ice carrier; 10) pump (mixer); 11) inspection ice; 12) the grille of the compressor compartment; 13) heat exchanger for beverage cooler.
The first enter to the cooling mode took 3 hours. 29 minutes, but the formed ice field was uneven and decreased in height. After analyzing the results of the first start of the beverage cooler, an insufficient amount of refrigerant in the system and instability of its operation were revealed. Refueling of the refrigeration
system with refrigerant by 20 g, and changing the location of the sensitive element of the thermostat (Fig. 2, c) allowed to stabilize its operation and form a uniform ice field.
a) b)
Fig. 2. Placement of the sensitive element on the evaporator of beverage cooler ON-90.
As a result of the second start of the refrigeration system, the output was 4 hours and 35 minutes. The operation of a full-fledged system, cooling of beverages on the research stand was checked (Fig. 3) which
includes additional equipment - beverage bottling system 8, 11 and 12, which is designed to cool the beverage before bottling.
Fig.3. Schematic diagram of an experimental station for testing a water cooler.
1-Hot water tank №1; 2- circulating pump; 3- Shut-off valves of the bypass; 4-Flowmeter; 5- thermometer; 6-warm water expansion tank; 7- mixer pump; 8- internal goose heat exchanger; 9- coil heat exchanger; 10-reservoir of working substance; 11- liquid supply regulator through the beverage bottling system; 12- angle valve of the bottling system; 13 - supercooled water expansion tank; 14-reservoir of supercooled water №2.
1t - Warm liquid; 1u - Equalizing bypass line; 1x - Cooled liquid; 1po - Supercooled liquid; 1x '- Cold coolant;
1t '- Warm coolant.
To regulate the supply of cooled liquid to the circuit, a bypass line with a ball valve 4 was installed. During the experiment, water from tank 1 (water in the tank at the temperature of the third climate class) was used as the cooled liquid [6, 9].
Warm water from the tank 1 is pumped out, passing through the pump 2, at the outlet through the bypass system 3 part of the water is returned to the suction line, and the other enters the flow meter 4 (meter installed to monitor the passage of water through
the cooling system). After measurement, the water enters with a flow rate of 1.5 dm3 / min. enters the coil heat exchanger 9, where it is cooled. After passing the coil heat exchanger, the cooled water enters the beverage bottling system where it is cooled in the heat exchanger 8. The main liquid control system 11; 12 is installed in the liquid bottling system. The supercooled water enters the expansion tank 13, where the temperature is checked. After data collection, the supercooled water is collected in the tank 14.
In the cooling circuit, heat from two heat exchangers is supplied to the ice field. The coils of the heat exchanger 9 are washed with a working substance that has a dynamic movement by means of a "stirrer pump" 7 and removes heat from them and washes the ice field. The ice field in turn acts as an accumulator of cold. Another heat exchanger is in the beverage bottling
system. Cold water from the tank 10 is supplied to it by means of a "stirrer pump" 7 at a rate of 2-2.5 dm3 / min where it removes heat from the heat exchanger 8, and returns to the reservoir of the working substance 10. Two heat exchanger designs were proposed for the water supercooling experiment (Fig. 4).
In the first case (Fig. 4, a) a heat exchanger with three circuits of the same length is proposed. The winding of the first circuit of the heat exchanger is in the lower part of the tank with the working substance, and the second above it. The windings 1 and 2 of the heat exchanger circuits have 6 turns and the same width. The third circuit is in the middle of the circuit of the first and second, and has 12 turns smaller in width. The length of each of the circuits of this heat exchanger is 5.6 m and is made of stainless steel tube 8*0.5 mm.
(a) (b)
Fig. 4 Beverage cooler heat exchanger. a - heat exchanger with equal length of circuits; in - the heat exchanger with various length of contours, 1, 2, 3
contours of the heat exchanger.
The second heat exchanger (Fig. 4c) is made of 3 circuits, each of which has 14 turns but different in width. This heat exchanger is made so that the second circuit is in the first, and the third in the second. In this heat exchanger, the length of the first circuit is 6.95 m, the length of the second is 5.6 m, and the third has a length of 4.88 m. All turns are made of a stainless steel tube of AISI 304, 8*0,5mm.
Thus, the experiment consisted of two stages. In the first part of the experiment, a heat exchanger with an equal heat exchange area was installed in the beverage cooler. The experiment was performed on each turn of the heat exchangers in turn. Each part of the test took place over a period of one hour with a coolant flow rate of 1.5 dm3/min.
Fig.5. Graph of temperature dependence on the flow rate of the cooled product (water) in the heat exchanger
with an equal heat exchange area of the structure (a).
After the experiment, the residual ice field was water cooler and in the tank №1 was heated to ambient thawed, and the working substance in the tank of the temperature (+ 25°C). After these manipulations, the
refrigeration unit was turned on for a period of 5 hours to enter the mode. The experiments were performed according to the requirements of PN-EN ISO 23953-1; 2005 Refrigeration equipment [1] and in compliance with the rules of DSTU 3888: 2015 Beer [4, 5]. General technical ideas. The results of the experiments are shown in Fig. 5.
The second part of the experiment was carried out with similar initial parameters of heat carriers, cooled liquid and environment, about which a heat exchanger with different heat exchange area was installed in the beverage cooler. According to the first part of the experiment, a graph of temperature dependence on fluid flow is constructed [10].
Fig. 6. Graph of temperature dependence on the flow rate of the cooled product (water) in the heat exchanger
with different heat exchange area of the structure (b).
Table 1.
The average derived values of the test of heat exchangers
Average values of operation of the water cooler on the heat exchanger with equal heat exchange area (a)
V; 1/ 5min. T min Average inlet temperature, °C Average outlet temperature, °C At subcoo1ing,°C
0 0 26,6 5,0 21,6
15 10 26,5 7,1 19,4
30 20 27,0 7,5 19,5
45 30 27,2 8,0 19,1
60 40 26,6 8,6 18
75 50 26,8 10,1 16,7
90 60 12,8 26,8 14
The average values of the water cooler on the heat exchanger with different heat exchange area (c)
V; 1/ 5min. T min Average inlet temperature, °C Average outlet temperature, °C At subcoo1ing,°C
0 0 26,1 5 21,1
15 10 26,5 6,3 20,2
30 20 26,7 6,9 19,8
45 30 27,0 7,2 19,8
60 40 26,8 7,2 19,6
75 50 26,4 7,9 18,5
90 60 26,6 9,5 17,0
Analysis of the results showed an advantage in temperature stability at different heat exchanger circuits with the same heat transfer surface (heat exchanger design (a)). However, visual inspection of the coolant and ice field revealed an uneven heat load on the ice field and as a result incomplete load on the evaporator and inadequate operation of the refrigeration system. To obtain a complete analysis of the heat exchangers, the average valuesof the temperatures obtained in the experiments are derived
and on their basis the dependences of the liquid flow rate on the arithmetic mean temperatures of table 1 are obtained. Analysis of the obtained values and comparison of the temperature difference shows the compliance of both heat exchangers with the required standards. The difference in temperature at the inlet and outlet of the cooled liquid at the end of the experiment does not exceed 10K, so when selecting a heat exchanger for a water cooler, the key factors were: compliance; temperature stability of the cooled liquid
at the outlet; cost. At the end of the selection of of production of HFC refrigerants, a retrofit and a refrigeration system components and taking into comparative analysis of the beverage cooler on account the restrictions on the use and gradual cessation refrigerants R404a and R290.
Fig. 7. Water cooler schedule on R404a. depending on temperature over time. 1 - temperature of the discharge pipe; 2 - temperature of the compressor casing; 3 - temperature of the end of condensation; 4 - temperature of the suction pipe; 5 - temperature in the ice field
The first part of the study was based on a ready- sensors for the METRONIC DL7 temperature made prototype that was created on R404a. The third monitoring system were connected to the refrigeration climate class was set in the research area, and five system.
Fig.8. Water cooler schedule for R290. Depend the temperature on time. 1 - Temperature of the discharge line; 2 - Compressor housing temperature; 3 - Temperature of the end of condensation; 4 - Temperature of the suction pipeline; 5 - Temperature in the ice field
The experiments were performed according to PN-EN ISO 23953-1; 2005 [1] without additional thermal loads from the consumer. The schedule includes changes in temperatures in the refrigeration system during the entry into operation (increase in the ice field) and several cycles of operation (Fig. 7). To obtain the results of the beverage cooler on the R290, the compressor was replaced with an Embraco Aspera
EMT6165U, the dehumidifier filter was replaced and the refrigerant was refilled with propane (Fig.8). The conditions for removing the operating parameters corresponded to the first parts of this experiment. Electricity was also measured during the experiments (16 hours). Logical results were obtained from the analysis of work schedules. The obtained and calculated results are entered in table 2.
Table 2.
Measurements of energy consumption N0-90
Refrigerant (charge amount) R404a (0,31kg) R290 (0,11kg)
Measurement time 16 hours 2,26 kW 1,85 kW
Calculated measurement of kW / day. 3,39 kW/day 2,775 kW/day
The study allowed to select the most suitable for the refrigeration system heat exchanger of the beverage cooler. Based on the results of the experiment, there is an obvious advantage in the performance of the heat exchanger with different heat transfer area (same for R404a and R290). This conclusion is justified not by the uniformity of heat supply to the ice field, and as a consequence of its uneven melting. A comparison of the operation of the beverage cooler on different refrigerants showed a decrease in the condensation temperature and lower energy consumption on the R290. Energy consumption on R290 was 20% lower than R404a. The refueling dose of the refrigeration system was significantly reduced by using R290. Studies of the beverage cooler have made it possible to develop a new concept of NO-90 and to introduce an efficient and standardized mode of operation of the system as a whole.
References
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4. Ukrainian National Standard DSTU 3888: 2015 Beer. General technical ideas.
5. Ministry Of Economy and European Integration of Ukraine / Order / of January 3, 2003 N 2 / About the statement of the Recommended norms of technical equipment of public catering establishments.
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