Design of Refrigeration Control System for Parallel Refrigerator Unit Based on PLC

In order to improve the refrigeration control efficiency and reduce the temperature fluctuation in the cold storage. In this paper, the refrigeration control system of the parallel unit of the cold storage is designed based on the upper and lower computers. The lower computer uses PLC to monitor the field parameters and control the execution of the field equipment. The upper computer uses HMI to realize the real-time monitoring, parameter display and alarm function during the operation of the cold storage, and uses the slide valve to adjust the energy of the compressor. The results show that the control system runs reliably and meets the control requirements of large cold storage.

The main indicators of compliance with the production standards and storage conditions of honey

The study presents an updated database on the impact of the main technological factors on the content of pollen grains and quality indicators of natural honey: diastase number, hydroxymethylfurfural content and invertase activity. The purpose of the research was to update the database on the impact of the main technological factors on the microscopy and quality indicators of natural honey: diastase number, hydroxymethylfurfural content and invertase activity. Based on the goal, the following tasks were solved: On the basis of the laboratory of the FSC of Beekeeping, production samples of honey were heated at 75 °C for 10 minutes, followed by natural cooling, and filtered through a filter with a cell size of 0.15 mm; they were stored in the production room for a year with a temperature fluctuation in the range from –1 °C to 32 °C. The relevance of the study is to study the main indicator of the quality of honey – invertase activity, changes in the value under the influence of technological and zootechnical factors, with its subsequent introduction into the state standard for natural honey. The scientific novelty of the study lies in the fact that for the first time the values of invertase activity indicators, the content of hydroxymethylfurfural after heating and filtration of honey were obtained. Methods. The study of the indicators was carried out in accordance with the methods of the state standard GOST 19792-2017. As a result, it was found that heating honey at 75 °C for 10 minutes followed by natural cooling contributes to a decrease in diastase activity by an average of 69.7 ± 6.43 %, a decrease in invertase by an average of 81.0 ± 2.37 %, and an increase in the content of GMF by an average of 79.1 ± 1.74 %. Honey filtration reduces diastase by an average of 11.1 ± 1.47 %, and invertase activity by an average of 11.3 ± 2.34 %. Storage of honey for a year with a temperature fluctuation from –1 °C to 32 °C contributes to a decrease in the activity of diastase by 51.3 ± 5.27 %, invertase by 61.0 ± 1.91 % and an increase in the content of hydroxymethylfurfural by an average of 82.9 ± 1.80 %.

Influence of temperature fluctuation on friction inside hydraulic cylinder

This paper considers variety of hydraulic actuators. Also it shows analysis of hydraulic equipment. The contribution is important due to the fact that it determines influence of temperature on friction in hydraulic equipment. The paper examines the factors of reducing the performance of hydrofected machines during operation at low temperatures. The importance of the work is due to the fact that the effects of temperature on friction in hydraulic equipment are considered. An experiment was also conducted, due to which the influence of temperature on the wear resistance of the hydraulic cylinder was revealed.

Plant Hardiness Zone Map in Korea and an Analysis of the Distribution of Evergreen Trees in Zone 7b

Background and objective: This study was conducted to establish a Plant Hardiness Zone (PHZ) map, investigate the effect of global warming on changes in PHZ, and elucidate the difference in the distribution of evergreen trees between the central and southern region within hardiness Zone 7b in Korea. Methods: Mean annual extreme minimum temperature (EMT) and related temperature fluctuation data for 40 years (1981 to 2020) in each of the meteorological observation points were extracted from the Open MET Data Portal of the Korea Meteorological Administration. Using EMT data from 60 meteorological observation points, PHZs were classified according to temperature range in the USDA Plant Hardiness Zone Map. Changes in PHZs for each decade related to the effects of global warming were analyzed. Temperature fluctuation before and after the day of EMT were analyzed for 4 areas of Seoul, Suwon, Suncheon, and Jinju falling under Zone 7b. For statistical analysis, descriptive statistics and ANOVA were performed using the IBM SPSS 22 Statistics software package. Results: Plant hardiness zones in Korea ranged from 6a to 9b. Over four decades, changes to warmer PHZ occurred in 10 areas, especially in colder ones. Based on the analysis of daily temperature fluctuation, the duration of sub-zero temperatures was at least 2 days in Seoul and Suwon, while daily maximum temperatures were above zero in Suncheon and Jinju before and after EMT day. Conclusion: It was found that the duration of sub-zero temperatures in a given area is an important factor affecting the distribution of evergreen trees in PHZ 7b.

A Preliminary Numerical Investigation of Thermal Mixing Efficiency in T-Junctions with Different Flow Configurations

When hot and cold fluids flow through a converging T-junction, rapid temperature fluctuations occur in the mixing region due to the thermal mixing of fluids. This temperature fluctuation causes thermal fatigue, which is responsible for the shortening of service life in a T-junction. Hence, the design of T-junction for thermal mixing requires not only superior mixing performance but minimize thermal fluctuation during mixing is also desirable. The objective of the present paper is to determine the thermal mixing performance at the mixing region of T-junction with two different flow configurations. Water, at different inlet temperatures, is used as a working medium and is assumed incompressible. Two types of flow configurations, namely intersecting and colliding regular T-junction with a sidearm pointing at 12 o’clock position have been evaluated in this paper. Realizable k-epsilon turbulence model was assumed, and its validity benchmarked against RANS and RSM-EB turbulence models. The thermal mixing efficiency of both flow configurations is calculated and compared. The results show that the thermal mixing efficiency of both intersecting and colliding mixing tee increases with the increase of distance and time. Intersecting tee shows higher temperature fluctuation than colliding tee at the mixing outlet, but colliding tee shows higher thermal mixing efficiency than intersecting mixing tee.