Local Air Conditioning Research Articles

Structure of Parabolic Trough Collector Model for Local Heating and Air Conditioning

Structure of Parabolic Trough Collector Model for Local Heating and Air Conditioning

Research on thermal comfort of commercial vehicle and economy of localized air conditioning system with thermoelectric coolers

In commercial vehicles, the power consumption of the traditional air conditioning system used to cool an entire cab is high. In most cases, there is only one driver in vehicle, so adjusting the local thermal environment around the driver can reduce much energy waste. In this paper, a localized air conditioning system based on thermoelectric cooling (TEC) devices was constructed, and its performance characteristic were studied to find the optimal operating conditions in practice. The relationship between the refrigeration power and the operating current of the device was studied. A bench test was carried out to evaluate the performance of the device and the accuracy of the simulation. This paper selected a commercial vehicle cab for the application of the TEC system. The thermal comfort of human body in cab and the economy of local air conditioning system was analyzed by the method of computational fluid dynamics. The driver’s thermal comfort was analyzed based on equivalent temperature and thermal comfort deviation. The results show that when the cooling power is 3000 W, the overall thermal comfort deviation of human body under local thermoelectric refrigeration is 7.94% higher than that under traditional refrigeration. When the duty ratio of the centrifugal fan governor is about 40%–60%, the semiconductor cooling device has excellent refrigeration performance and low energy consumption, which can not only ensure the thermal comfort of the driver but also reduce the energy consumption of the air conditioner.

ФОРСАЙТ ПІДВИЩЕННЯ ЕНЕРГОЕФЕКТИВНОСТІ БУДІВЕЛЬ НА БАЗІ ЕНЕРГОХАБА УНІВЕРСИТЕТУ

The article reveals the essence of the key motivation drivers to save energy and increase the energy efficiency in higher education institutions. In particular, a low level of interest of higher education institutions in the implementation of strategies to reduce energy consumption has been observed. The findings suggest that the lack of interest in energy saving is primarily affected by budget legislation since the energy cost calculation was based on the consumption norms for a particular budgetary institution and the current (planned) electricity and heat tariffs. Recently, it has been decided that from now on universities will not obtain budget funding to cover utility costs; the amount of subsidies from the Ministry of Education and Science of Ukraine for the implementation of the government objectives will comprise regulatory costs for public service provision according to the student contingent. Standard property maintenance costs will not be covered by the Ministry anymore which will impose the burden of paying the utility bills upon the University’s gross income. Hence, there is a need to take efforts to enhance energy efficiency and energy saving in higher education institutions which was implemented using a foresight methodology. Within the scope of this study, the foresight project to improve the energy efficiency of buildings in the frameworks of the University energy hub is based on the following calculations: thermal energy consumption for heating public buildings, estimated hourly heating load to ensure heating in the building, verifying the feasibility of heating standby regulation, measuring energy savings through the creation of an automated heat supply station, as well as annual savings in monetary terms. In order to save resources and boost energy efficiency based on the University energy hub using an automated heat supply station, the study offers a mathematical toolkit to justify the choice of minimum and maximum values of optimal microclimate parameters; reduce infiltration, increase the efficiency of indoor air distribution; optimal modes of local air conditioning, preheating and cooling; utilizing of "waste" and natural heat and cold; "combining" microclimate systems with other systems; improving automation devices in technical systems. It is argued that increasing the energy efficiency of heating systems in University buildings on the basis of its own energy hub will contribute to gaining significant savings in thermal energy for heating and significantly reduce carbon dioxide emissions into the environment. In addition, the study reveals that the cost of thermal energy for heating depends upon a building design, modernization quality, reconstruction and insulation, applied building materials, spatial planning solutions, the presence or absence of control and automated systems, maintenance systems and attitude of owner’s attitude to innovations. The conclusions summarize that the cost of thermal energy can vary significantly in buildings of the same type.

Proposal of Jet Control Method by Elucidating Inclined Impact Jet Characteristics on Local Air Conditioning System

We have been developing a local air conditioning system which supplies airflow locally to users. This system directs a composite jet to users, created by colliding jets from nozzles on either side of a wall. However, Coanda effect near the nozzle caused instability at the collision point of the two jets, resulting in the composite jet not being delivered to the user. This research aims to control passively the suppression of Coanda effect by changing the wall shapes near the nozzle to convex type or concave type. The effects of convex thickness and concave groove width on the suppression of Coanda effect were examined by numerical simulation and flow visualization. As a result, Coanda effect becomes larger as the jet velocity slows down, and as a result, the two jet collision points oscillate greatly to the left and right. Moreover, Coanda effect can be suppressed if the thickness and groove width were larger, and consequently the composite jet was centered. On the other hand, the jet was influenced by the wall in the smaller sizes, and the composite jet was shifted to the left and right.

Experimental investigation of occupants’ thermal sensation under a personalized ventilation system

By considering the importance of providing proper indoor environment conditions for occupants and also due to energy costs, one of the solutions for indoor local air-conditioning is Personalized Ventilation System (PVS). In this paper, the occupants’ thermal sensation was experimentally studied for body segments that are mostly affected by the PVS. The local sensation of head, chest, arm, and hand at two supply air temperatures of 16 and 32°C were investigated. Eight volunteer subjects participated in this survey. The subjects reported the most thermal satisfaction on their hands. Also, the arms were the segments with the coolest thermal sensation (-1.28, between slightly cool and cold). Results indicate that the head’s thermal sensation at both supply air temperatures was neutral and the hand was the only body part that experienced warm thermal sensation during the test. Also, by increasing the supply air temperature to 32°C whole body thermal sensation changed from -0.46 to -0.09 on the seven-point scale, which means that the cooling system worked properly for occupants’ cooling. In this system, cooling occurred at 32°C instead of the common 16°C supply air temperature, which results in energy-saving and decreases annual running costs.

Application of entransy method in heat exchanger networkoptimization for low-grade waste heat utilization

<p indent="0mm">Efficient utilization of low-grade industrial waste heat is of great significance to improve the efficiency of energy utilization and to reduce CO₂ emission. Energy system integration and corresponding heat exchanger network optimization are effective solutions. The entransy method is suitable for quantifying the irreversibility of the heat exchange process and guiding and evaluating heat exchanger network optimization. However, there are relatively few cases in which the entransy method is applied to the heat exchanger network optimization for waste heat utilization. In this study, the waste heat utilization of steam condensate in an industrial park through a heat exchanger network was analyzed based on the entransy method. By reducing the entransy dissipation of the heat exchange process of the condensate, the existing heat exchanger network was optimized, and the high-grade waste heat was utilized by an absorption chiller for local air conditioning demands. As a result, the discharge of high-grade waste heat was converted to the discharge of low-grade waste heat. The optimized heat exchanger network guided the redesign of the actual heat exchanger network. The testing results showed that the cooling effect of the developed seawater cooled absorption chiller reached <sc>3430 kW</sc>, with a coefficient of performance of 0.76. The entransy dissipation of the heat exchange process of the condensate was reduced by 57.3%. The thermal efficiency and exergy efficiency of the heat exchanger network were increased by 55.8% and 81.1%, respectively. These results demonstrate that the entransy method is valid in the application of low-grade waste heat utilization through heat exchanger network optimization.

Optimal Design of Integrated Chiller Capacity with Ice Thermal Storage for Commercial Buildings through Cooling System Cascade Analysis

Chilled water air conditioning system is used to supply cooling systems in large capacity for industrial processes and commercial buildings. Air conditioners contribute more than 60 percent of electricity consumption in buildings. District Cooling System (DCS) technology comprises a central chiller plant which provides advantage compared to local air conditioning system. It has higher efficiency, uses less power in system operation, allows more usable space in buildings, and can be operated with minimum manpower while handling same amount of cooling load. The integration of a chiller with ice thermal storage (ITS) offers more operational flexibility while reducing space cooling expenses. This paper presents a systematic framework for design and operation of District Cooling Plant (DCP) comprising an integrated chiller and ice thermal storage system. The Cooling System Cascade Analysis (COSCA) based on pinch analysis is constructed to determine the chiller optimal size and ice thermal storage capacity. The District Cooling System configuration for this study comprises a cooling tower, chiller (centrifugal, variable centrifugal, glycol) and ice thermal storage system. The application of this technique to fulfil 66,284 refrigerant tonne hour (RTH) cooling load demand from commercial buildings reveals the optimal capacity of the chiller is 3068.91 refrigerant tonne (RT), ice tank rating at 989 refrigerant tonne (RT) and ice tank capacity is 9892.75 refrigerant tonne hour (RTH).

A study of new local heating and air conditioning schemes based on the Maisotsenko cycle

Significant consumption of energy resources in the production of heat in the winter season and air conditioning in the summer season is the main problem of municipal heat-and-power engineering. Therefore, local energy-efficient heating systems and climatic heating and cooling systems based on renewable energy sources are becoming increasingly important. The heat pumps, based on the Rankine cycle, which use the energy of atmospheric air, soil, and wastewater, as well as air conditioning systems, based on the Maisotsenko cycle, using the psychrometric energy of the environment, have become widespread in recent years. Theoretical analysis shows that a combination of these cycles makes it possible to achieve high energy efficiency and create fundamentally new systems of heating and cooling the living spaces. This paper presents the results of a comparative experimental study of two heat supply and cooling schemes based on a combination of the Maisotsenko and Rankine cycles. An experimental bench of the combined cycle with thermal power of 28 kW with the power of the heat pump of 3 kW was developed for the experimental study. A serial M-cycle heat-and-mass exchanger manufactured by Coolerado Corporation, USA, was used in the design of the bench. Studies have shown high energy efficiency of both heat supply schemes which was determined by the coefficient of performance (COP): 6.3–7.21 for the first scheme and 7.44–9.73 for the second one. When conditioning the room air, the Rankine heat pump was not used, so the energy was consumed solely by the fan to pump air through the M-cycle heat-and-mass exchanger and the air conditioning system. In this case, the coefficient of performance was 10.49–16.32

Thermal simulation and cooling load analysis in the apartment unit through building construction elevation review

Air conditioning systems constitute one kind of essential utility at a building. They still could be decreased its electrical cost consumption by way of insistent to continue the performance of its room air cooler system. The achievement of air conditioning system mentioned is very determined by the airflow pattern inner the room. Based on the airflow pattern which is raised furthermore it will be deliberated the cooling load which is determine cooling electricity costs. Construction elevation consideration will be carried out in the framework to obtain the difference of thermal condition each building level. The parameter mentioned is interesting to analyses due to the effect of sun heat will very dependent to the constructions elevation. Methodology which is to be used remains within practice the numeric simulation. The measuring of air temperature directly by means of censors also implemented within several level of construction elevation. The outcome of air temperature measurement will be used as the input value to the numeric simulation execution in the apartment unit with the local air conditioning system. It is obtained the thermal condition and cooling load of local air conditioning system in the apartment building unit within atypical floors.

Choice of sanitary-indicative microorganisms for the assessment of the safety of split-systems

Purpose of work is a compilation of data about the microflora which colonizes a split-system, with the aim of selection of sanitary-indicative microorganisms, whose presence in the sample would indicate to the need for cleaning and disinfection of split-systems. In the article there were used data of five years author's scientific inquiry, related to the prevention of respiratory diseases, associated with the usage of a local air conditioning systems. We also use the data from the literature. For selection of "indicative" microorganisms, we proposed the usage of nine criteria, each of them have numeric value from 0 to 3 points (risk for health, prevalence rate of the disease, epidemiological link, speed of split system's colonization, difficulty of cultivation, resistance in the environment, resistance to disinfectants, frequency of detection in home air conditioning systems, frequency of detection in air conditioning systems of public buildings). After the calculation Pseudomonas aeruginosa and Staphylococcus aureus received maximal score (20 points). Therefore, these two types of bacteria are indicative microorganisms. The detection of these microorganisms in split systems will indicate to the contamination of air-conditioning system. This microflora also is a criterion of cleaning and disinfection quality--presence of these microorganisms in the samples after this process will mean that the processing of air conditioning systems was performed poorly. Split systems are very faster colonized by conditionally pathogenic and pathogenic microflora. To prevent the possible hazard for population's health it is necessary to develop the normative base, according to which sanitary-and-hygienic control over the split-systems working must be carried out. Proposed criteria suggest that Pseudomonas aeruginosa and Staphylococcus aureus are indicative microorganisms, and it's identification in the air-conditioning system would mean risk for health and necessity for cleaning and disinfection.

МЕТОДОЛОГІЧНІ ПІДХОДИ ДО ВИЗНАЧЕННЯ ХОЛОДОПРОДУКТИВНОСТІ СИСТЕМ КОНДИЦІЮВАННЯ ПОВІТРЯ ЗА ЗМІННИХ КЛІМАТИЧНИХ УМОВ

One of the most attractive reserves for improving the energy efficiency of air conditioning systems is to ensure the operation of refrigeration compressors in nominal or close to nominal modes by selecting a rational design heat load and distributing it within its design value according to the behavior of the current heat load under variable current climatic conditions to provide the maximum or close to maximum annual cooling capacity generation according to cooling duties of air conditioning. In the general case, the overall range of current thermal loads of any air conditioning system includes a range of unstable loads associated with the precooling of ambient air with significant fluctuations in cooling capacity according with current climatic conditions, and a relatively stable range of cooling capacity consumed to further reduce air temperature from a certain threshold temperature to the final outlet temperature. It is quite obvious that a stable range of heat load can be ensured within operating a conventional compressor in a mode close to the nominal mode while precooling the ambient air with significant fluctuations in heat load requires regulation of the cooling capacity through the use of a variable speed compressor. Thus, in response of the behavior of the change in current heat loads, any air conditioning system, whether the central air-conditioning system with its heat procession in a central air conditioner, or a combination thereof with a local recirculation system of indoor air, essentially consists of two subsystems: pre-cooling the ambient air and then cooling it to the set point temperature. The proposed method of distribution of design heat load depending on the behavior of the current heat load is useful for the rational design of central air conditioning systems and their combined versions with the local air conditioning system.

Development of Heating and Cooling Local Air Conditioning System for Houses

Centralized air conditioning systems are widely used in buildings at present. In these conditioners, the outside air gets required temperature, humidity, purity, and other features, necessary for creating comfort microclimate in inside areas of houses, and by the help of fans and air ducts the processed air moves to all rooms of a building. As a result, the creation and maintenance of comfort conditions in buildings become complicated and expensive activity. From this point of view, it is becoming more expedient to install local air conditioners in each room instead of single central one for the whole building. For this reason new local air conditioner is developed.

コアンダ効果を利用した局所空間空調(第3報)実大実験と設計への応用

コアンダ効果を利用した局所空間空調(第3報)実大実験と設計への応用

コアンダ効果を利用した局所空間空調 : 第1報-温噴流を用いた暖房時の基本特性(模型実験)

コアンダ効果を利用した局所空間空調 : 第1報-温噴流を用いた暖房時の基本特性(模型実験)

コアンダ効果を利用した局所空間空調 : 第2報-理論的解析

コアンダ効果を利用した局所空間空調 : 第2報-理論的解析

Microbial contamination of Raw meat in Retail Shops

This study was based on collecting 120 random samples of raw meat from Local markets, butcher shops, super markets and air condition shops at Kafer El-sheikh city (30 of each).The collected Samples were subjected to microbiological examination including Mesophilic count, cloiforms count and isolation and identification of E.coli and Salmonellae. the obtained results revealed that the mean value of Mesophilic count were 1.03 × 105 , 3.17 × 104 , 2.09 × 104 and 1.84 × 104 CFU/g at local market, butcher shop, super market and air condition shops respectively and the mean value of cloiforms count were 3.7 × 103, 1.38 × 103 , 1.04 × 103 and 4.54 × 102 CFU respectively. In addition, the incidence of E.coli isolated from examined samples were 23.33, 13.33, 6.67 and 3.33% respectively. While the incidence of Salmonellae isolated from the examined samples were 20, 16.67, 10 and 3.33% respectively at local market, butcher shops, super market and air condition shops.

Development of ZL400 Mine Cooling Unit Using Semi-Hermetic Screw Compressor and Its Application on Local Air Conditioning in Underground Long-Wall Face

Abstract Aiming at heat injuries occurring in the process of deep coal mining in China, a ZL400 mine-cooling unit employing semi-hermetic screw compressor with a cooling capacity of 400 kW is developed. This paper introduced its operating principle, structural characteristics and technical indexes. By using the self-built testing platform, some parameters for indication of its operation conditions were tested on the ground. The results show that the aforementioned cooling unit is stable in operation: cooling capacity of the unit was 420 kW underground-test conditions, while its COP (coefficient of performance) reached 3.4. To address the issue of heat injuries existing in No. 16305 U-shaped long-wall ventilation face of Jining No. 3 coal mine, a local air conditioning system was developed with ZL400 cooling unit as the system’s core. The paper presented an analysis of characteristics of the air current flowing in the air-mixing and cooling mode of ZL400 cooling unit used in air intake way. Through i-d patterns we described the process of the airflow treatment, such as cooling, mixing and heating, etc. The cooling system decreased dry bulb temperature on working face by 3°C on average and 3.8°C at most, while lowered the web bulb temperature by 3.6°C on average and 4.8°C at most. At the same time, it reduced relative humidity by 5% on average and 8.6% at most. The field application of the ZL400 cooling unit had gain certain effects in air conditioning and provided support for the solution of mine heat injuries in China in terms of technology and equipment.

Optimization of Thermal Stability of Atrium Based on Computational Modeling

The article deals with analysis of the heat balance and temperature microclimate of indoor space of a four-storey building atrium. With regard to the anticipated thermal loads in all functionally connected rooms, investor made a request to verify the thermal stability of the atrium before the implementation stage. Atrium and adjacent rooms are a geometrically complicated inner space which cannot be solved by analytical methods to ensure the required temperature conditions in occupied zone. This led to the creation of a mathematical model of the atrium with the current project solution. The result of the simulation of the existing solutions is that there is not complied desired air temperature in the occupied zone. For this reason, it was developed optimization of existing variant. Optimization was performed in steps as changing temperature of the central air conditioning system, changing number of units and performance of local refrigeration air conditioning. The conclusion of this paper is to evaluate the thermal profiles of temperature stratification in the atrium area and request the required cooling performance of the ventilation system. The article attempts to use computer modelling as a tool for the placement and performance design of ventilation equipment.

Evaluation of Isocyanates Concentration in the Air of the Foam-producing Section in a Car Manufacturing Company

Methylene diphenyl diisocyanate (MDI) is the most used isocyanate in the manufacture of polyurethane foam, and it is one of the major causes of occupational asthma. Therefore, in this research, the MDI concentration in the air of the foam- producing section in a car manufacturing company was assessed. To determine MDI concentration, Health and Safety Executive (HSE) air sampling and analysis method, No. 49, was used. In the method, a certain volume of the workplace air was drawn with an impinger content of dimethylformamide and diluted hydrochloric acid. By doing this, organic isocyanates were extracted followed by reactions of hydrolysis to similar amines. The final solution was used for the absorption by the UV-VIS spectrophotometer. Evaluation of MDI in the summer showed that MDI concentration in all parts of the workplace was less than the threshold limit value, and only when local ventilation system and air condition system (air suppliers) were off was the concentration of MDI in the foam injection station higher than the threshold limit value. On the other hand, it is probable that air pollution increases in winter due to closing of doors of the foam-producing section and turning off of the air-conditioning system. Therefore, permanent air-handling and local ventilation is essential when working in the workplace in order to prevent respiratory, skin, eye, and gastrointestinal diseases.

A survey on different radiative and cloud schemes for the solar radiation modeling

Six different schemes for solar radiation forecasting are presented and validated for three Italian sites with 1year of solar ground based measurements. The schemes differ for the global (IFS/ECMWF, GFS/NCEP) and local area model (LAMI, RAMS), for the implemented radiative scheme, for the use of an off-line Radiative Transfer Model and also for the cloudiness treatment. The performances of the models have been evaluated not only in clear or cloudy conditions, but in presence of specific types of clouds, detected with the SAFNWC/MSG cloud type software. The influence of local air condition has been confirmed, because of the best results for the site characterized by low levels of aerosols.On average, the relative MAE ranges from 11% to 17% and RMSE from 21% to 28% for the best model when all data have been used. According to the performance evaluation depending on cloudiness, the main errors on forecast occur in presence of very thick clouds, which constitute about the 20% of the cloudy events, but the relative MAE is about 120%. In clear sky conditions the relative MAE is about 5–9% for all the stations and models.A correct interaction between the radiative scheme and the microphysics plays an essential role in the solar forecasting, and the ability to analyze the results in relation to the type of clouds allows you to give an insight into this interaction.