Range Of Outdoor Temperatures Research Articles

ТЕПЛОМАССООБМЕННЫЕ ПРОЦЕССЫ В ИСПАРИТЕЛЬНОМ БЛОКЕ ВОЗДУШНОГО ТЕПЛОВОГО НАСОСА

Heat pump installations and the possibility of their application in engineering systems are considered. This allows expanding significantly the possibilities of using renewable energy sources, as well as waste heat from various technological processes in engineering systems for creating a microclimate. Air heat pumps are the most promising, but their use in regions with a cold climate is limited due to condensation of moisture vapors on the cooling line of the evaporation unit with subsequent formation of ice, which reduces the efficiency of the installation. In this paper, an upgraded evaporative unit of an air heat pump with a MOVEBIT ice removal system is considered. Taking into account the design of the heat exchanger, which includes a magnetostrictive radiator unit, the influence of heat and mass transfer processes in the evaporation unit on the efficiency of the heat pump unit in a wide range of outdoor temperatures is considered. A criterion equation has been obtained for calculating the heat transfer coefficient in the evaporation unit depending on the hydrodynamic conditions of the process and the thermophysical parameters of the air environment. This equation allows to calculate the heating capacity and cooling capacity. In addition, to determine the coefficient of energy transformation of a heat pump installation at all stages of the life cycle of engineering systems. The dependence of the influence of temperature and relative humidity on the kinetics of ice formation is obtained. This provide calculation the operating time of the installation between the cycles of switching on the radiator to destroy the ice. Based on the research results, computer programs have been developed for controlling the main thermal parameters of an air heat pump with a MOVEBIT system and an electrical part of a magnetostrictive radiator in a wide temperature range.

К РЕШЕНИЮ ЗАДАЧИ КОЛИЧЕСТВЕННОГО РЕГУЛИРОВАНИЯ В СИСТЕМАХ ТЕПЛОСНАБЖЕНИЯ

The quantitative regulation of the heat supply process has a number of significant advantages and is widely used abroad. This method of regulation is also used in the Russian Federation. At the same time, the algorithmization of quantitative regulation is currently still quite problematic and requires further development. For example, the literature data on the algorithm proposed by E.Ya. Sokolov are characterized by the “omission” of the procedures of inference and justification, which is particularly undesirable for educational applications. In addition, the algorithm does not work across the entire range of thermal loads (outside temperatures). Purpose of the study. To develop an algorithm for quantitative regulation in terms of its subsequent use as part of the algorithmic support of an automated control system (ACS) for heat supply. Materials and methods. Literature data on the issue under consideration was analyzed. Using models of heating systems and heat losses of buildings, we compiled a balance equation that makes it possible to find the necessary coolant flow for heating. Results. A detailed substantiation and derivation of the algorithm for quantitative regulation of heat supply according to the heating load is proposed, and its characteristics were analyzed. The conditions for the physical feasibility of heating are taken into account. The algorithm as a whole is represented by a two-interval formula; in the second range of outdoor temperatures, the heat carrier flow rate is calculated based on the condition that the return water temperature should be noticeably higher than the indoor air temperature of the heated premises. However, when regulating the heat carrier flow in the second interval, an overestimated power of the heating system will be observed, i. e. some overshoot is possible. It is shown that with an increase in the minimum allowable value of the return water temperature, the range of outdoor temperatures in which regulation is possible in the first interval (ideal regulation without overflow) noticeably narrows, and when the water temperature in the supply line decreases, conversely, it expands. Conclusion. The results of the work can be used to develop algorithmic support for automated control systems for heat supply.

Operation Parameters Variation of Air Source Heat Pump According to the Outdoor Temperature

Air source heat pumps (ASHP), known as energy efficient systems, emerge as environmentally friendly and economical solutions for building heating. Unfortunately, the operating parameters of ASHPs and accordingly their performance are directly affected by the daily and seasonal temperature changes of the outside air. In this study, change in operation parameters of a selected ASHP with 3.4kW nominal heating capacity is investigated with a calculation method based on the logarithmic mean temperature difference, between -10°C to 18°C outdoor temperature range with 2°C steps, at constant compressor power. The study is verified with published COP data of the manufacturer. Results are shared with graphs that give the variation of refrigerant evaporation and condensation temperature and pressure, COP, and condenser heating load according to outdoor air temperature. A raise from -10°C to 18°C in outdoor temperature, increases the COP value from 3.38 to 5.49. Detection of the increase in evaporation pressure in parallel with the outdoor temperature may allow easy control of the refrigerant charge level with a manometer. This study can be a useful guide for researchers who aim to determine the outdoor temperature dependent operating parameters of an ASHP and for technical personnel who need this information in fields.

Energy saving, indoor thermal comfort and indoor air quality evaluation of an office environment using corner impinging jet ventilation

The performance of a corner based impinging jet ventilation system (CIJV) in an office environment was evaluated numerically. The evaluation was done both in terms of the local thermal comfort and the local indoor air quality. Three different inlet configurations were tested for a range of outdoor temperatures that included both winter and summer conditions. In terms of indoor air quality, the results showed that CIJV performed better than a traditional mixing system. The study also revealed that CIJV creates a stronger temperature stratification in summertime compared to wintertime. When evaluating the energy saving potential the results showed a possible reduction of 7% for the ventilation flowrate when the outdoor temperatures were between −15 °C and −5 °C, 8% when the outdoor temperatures were between 0 °C and 10 °C and 9% when the outdoor temperatures were between 15 °C and 25 °C.

Conditions for the formation of ice dams on pitched roofs of buildings with cold attics

Introduction. The article describes the mechanism of ice formation on the roofs of buildings with pitched roofs and cold attics.
 Materials and methods. The authors developed a model and a heat balance equation for an unheated attic room and proposed a set of measures to normalize the temperature and humidity modes in unheated attics.
 Results. The study demonstrates dependences between the air temperature in the attic and the outdoor air temperature before and after the implementation of the proposed set of measures designated to normalize the temperature and humidity modes. The findings suggest that after the insulation of (1) enclosing structures separating a cold attic from heated rooms, (2) the walls of ventilation ducts, crossing the attic space and (3) the pipelines of the down-feed heating system, the outdoor temperature range is significantly reduced, which reduces the likelihood of roof icing.
 Conclusions. In addition, the implementation of the proposed set of engineering and technological measures allows not only increasing the thermal insulation of enclosing structures and pipelines of a heating system, but also reduces thermal energy losses in transmission and the consumption of thermal energy in a building during a cold season, improves the indoor climate parameters on the upper floors of a building, reduces the risks of damage to the roofing during mechanical snow removal, thereby increasing the maintenance period of structural and enclosing elements of the roof.

Improvement of lithium-ion rechargeable battery (LIRB) for Electric Ships

The rapid improvement of lithium-ion rechargeable battery (LIRB) has given a powerful impetus to the development of environmentally friendly, powerful and universal for use on ships and underwater vehicles. The practice of building electric ships for many years has confirmed the effectiveness of electric propulsion for many types of vessels. Organically, electric propulsion fits into icebreakers and those vessels whose operation is associated with increased maneuvering modes and variable loads on propellers. LIRB has been actively used on ferries operating in a wide range of outdoor temperatures. On diesel-electric submarines (DES), the use of rechargeable batteries is traditional and is the main source of electricity. The subsequent development of new sources of electricity, the improvement of power semiconductor devices and microelectronics has led to the successful implementation of ideas for the construction of fully electric offshore facilities.

Normal stress distribution of timber-concrete composite panels with an adhesive shear connection under thermal and humidity loadings

Humidity and temperature conditions have a substantial influence on the stresses and total deformation of timber-concrete composite panels, especially in terms of the high rigidity of the shear connection. In the present research, the normal stresses that resulted from the hygrothermal load of timber-concrete composite panels with an adhesive shear connection were analyzed. Three timber-concrete composite panel specimens were placed in controlled climate conditions. Strains in two orthogonal directions were measured. The stress distribution resulted from an approximate analytical calculation model. The results show that the highest stresses occurred near the shear connection. An increase in timber moisture content by 2.1% was predicted to result in exceeding the flexural tensile strength in the concrete perpendicular to the timber grain direction. At an outdoor temperature range, stresses influenced only by the temperature alone will possibly not cause a failure of timber or concrete. Under winter environmental conditions, the stress in timber can possibly reach 12% of the bending strength of the timber used.

ТЕОРЕТИЧЕСКОЕ ОБОСНОВАНИЕ УГЛОВОЙ КОРРЕКЦИИ ВЕКТОРА ПОТОКА СТРУИ ПРИТОЧНОГО ВОЗДУХА В СИСТЕМАХ ВЕНТИЛЯЦИИ ПРОМЫШЛЕННЫХ И СЕЛЬСКОХОЗЯЙСТВЕННЫХ ОБЪЕКТОВ

During the heating period, the supply air temperature is lower than that in industrial premises, and the cooled air is denser. Entering a warm room, it tends to move downward. This condition leads to the formation of chilled and stagnant zones. The article presents a theoretical study on the possibility of ensuring the maximum propagation range of a non-isothermal supply air jet by angular correction of the fl ow vector at the outlet of the ventilation unit. Based on the theory of free air distribution, the author analyzed and graphically visualized the fl ow trajectories of the supply air from the combined climate control unit with heat recovery in the production room in the range of outdoor temperatures from +10 to –40°C. Given the time period of outdoor temperatures, fl at sections of a three-dimensional graph were built with a step of 10°C in the range from +10 to –30°C. The author found that the maximum service area of the installation is limited by the propagation range of the supply air jet. The area can be increased by changing the direction of the fl ow vector by an angle ranging between 0 and 34°. The value of the inclination angle of the fl ow vector of the supply air jet is determined by the obtained approximation dependency. Considering the regulation of the fl ow vector, the author used the formula of M.Z. Pechatnikov to determine the propagation range of a limited axisymmetric jet. The studies carried out made it possible to establish the relationship between the propagation range of the supply air jet of the installation and the outside temperature, the inclination angle of the fl ow vector, and the theoretical variation range of the inclination angle of the fl ow vector, ranging between 0 and 34°.

ТЕОРЕТИЧЕСКОЕ ОБОСНОВАНИЕ УГЛОВОЙ КОРРЕКЦИИ ВЕКТОРА ПОТОКА СТРУИ ПРИТОЧНОГО ВОЗДУХА В СИСТЕМАХ ВЕНТИЛЯЦИИ ПРОМЫШЛЕННЫХ И СЕЛЬСКОХОЗЯЙСТВЕННЫХ ОБЪЕКТОВ

During the heating period, the supply air temperature is lower than that in industrial premises, and the cooled air is denser. Entering a warm room, it tends to move downward. This condition leads to the formation of chilled and stagnant zones. The article presents a theoretical study on the possibility of ensuring the maximum propagation range of a non-isothermal supply air jet by angular correction of the fl ow vector at the outlet of the ventilation unit. Based on the theory of free air distribution, the author analyzed and graphically visualized the fl ow trajectories of the supply air from the combined climate control unit with heat recovery in the production room in the range of outdoor temperatures from +10 to –40°C. Given the time period of outdoor temperatures, fl at sections of a three-dimensional graph were built with a step of 10°C in the range from +10 to –30°C. The author found that the maximum service area of the installation is limited by the propagation range of the supply air jet. The area can be increased by changing the direction of the fl ow vector by an angle ranging between 0 and 34°. The value of the inclination angle of the fl ow vector of the supply air jet is determined by the obtained approximation dependency. Considering the regulation of the fl ow vector, the author used the formula of M.Z. Pechatnikov to determine the propagation range of a limited axisymmetric jet. The studies carried out made it possible to establish the relationship between the propagation range of the supply air jet of the installation and the outside temperature, the inclination angle of the fl ow vector, and the theoretical variation range of the inclination angle of the fl ow vector, ranging between 0 and 34°.

ОСОБЕННОСТИ ПРИМЕНЕНИЯ ВЕРТИКАЛЬНОЙ ФРЕЗЫ ДЛЯ ОБРАБОТКИ ПОЧВЫ В МЕЖДУРЯДЬЯХ МАЛИНЫ

When tilling the soil with a vertical-rotary limiter of the raspberry row width, rotating knives perform its transverse transferring. In this regard, it is advisable to fi nd the means to control the process. The study revealed the infl uence of the design parameters of the raspberry row width limiter on the pattern and degree of the lateral displacement of the cross-section of the cultivated soil strip. The authors assessed the intensity of the process of transverse soil redistribution by comparing the positions of the gravity centers of the treated strip cross-section before and after the tillage operation. The studies analyzed medium and heavy loams with a humus content of less than 2.5% and a wide range of variation in moisture content and contamination of the treated strip. With a rotor diameter of about 900 mm, the lateral displacement of the gravity center of the strip cross-section varies within the range of 50…100 mm. The authors found that the lateral displacement control of the soil layer is possible at a constant forward inclination angle of the rotation axis of the knife rotor, which is equal to 18º. This can be done by changing the lateral inclination angle of the specifi ed axis towards the row spacing center in the range between 10 and 20º. As a result, a signifi cant portion of the discarded soil returns to the treated strip surface, minimizing its outside throw-off and eliminating the possibility of injuring the raspberry shoots. The limiter proposed by the authors has a longitudinal baffl e installed at an angle to the vertical with a minimum energy intensity of the process. It helps to maintain the cross-section of the surface of the row spacing of raspberries in a leveled state throughout the entire life of the plantation.possibility of ensuring the maximum propagation range of a non-isothermal supply air jet by angular correction of the fl ow vector at the outlet of the ventilation unit. Based on the theory of free air distribution, the author analyzed and graphically visualized the fl ow trajectories of the supply air from the combined climate control unit with heat recovery in the production room in the range of outdoor temperatures from +10 to –40°C. Given the time period of outdoor temperatures, fl at sections of a three-dimensional graph were built with a step of 10°C in the range from +10 to –30°C. The author found that the maximum service area of the installation is limited by the propagation range of the supply air jet. The area can be increased by changing the direction of the fl ow vector by an angle ranging between 0 and 34°. The value of the inclination angle of the fl ow vector of the supply air jet is determined by the obtained approximation dependency. Considering the regulation of the fl ow vector, the author used the formula of M.Z. Pechatnikov to determine the propagation range of a limited axisymmetric jet. The studies carried out made it possible to establish the relationship between the propagation range of the supply air jet of the installation and the outside temperature, the inclination angle of the fl ow vector, and the theoretical variation range of the inclination angle of the fl ow vector, ranging between 0 and 34°.

The first operation results of the gas turbine unit M701F4 as a part of CCP-410 of the Krasnodar TPP after major overhaul

The article contains the reconstruction results of the M701F4 gas turbine unit of the Krasnodar TPP, where it has been in operation since 2011. In May 2019, it was overhauled with the replacement of the gas turbine working blades. In the first two rows, the blades of a new design were used. This allowed reducing the air flow for cooling and forcing the combustion chamber. For research we obtained archival indicators of a standard automation system. They were selected for the periods of operation, which lasted from June 2018 until the moment of major repairs (May 2019) and from June 2019 to January 2020. Data processing was carried out in accordance with State Standard R 55798-2013 (ISO 2314: 2009). The study showed that the reconstruction led to an increase in maximum capacity in the entire range of outdoor temperatures. Under normal conditions and standard air temperature at the compressor inlet equal to +15 °C, there is an increase by 14.4 MW or by 4.6%. The temperature of the combustion products also increased, the increase was about 15 °C in the range of outdoor temperatures from +5.6 to + 20.0 °C. The change in the consumption of combustion products is insignificant. We also estimated an increase in the efficiency of electricity generation. It is at the level of 0.5%.

Deriving sequences of operation for air handling units through building performance optimization

Operational parameters of air handling units (AHUs) play an important role in the energy and comfort performance of commercial buildings. Current guidelines to determine these parameters are based on heuristics and are not informed by formal optimization. This paper presents a building performance optimization method to derive sequence of operations for multi-zone AHUs. To this end, 27 variants of a generic EnergyPlus office building model are built representing three levels of occupancy, envelope, and HVAC capacity scenarios. The supply temperature, morning start time, and economizer settings of the model are optimized for the 27 scenarios by using a genetic algorithm. The results highlight that optimal supply temperature setpoints transition from ∼12°C to a range of ∼16°C to ∼20°C over an outdoor temperature range of ∼20°C to ∼0°C. Energy savings are estimated as ∼20% relative to a reference case with a constant supply temperature and preheating/precooling period.

교류 전동차 주회로 차단기 동작특성 연구

This paper presents an analysis of the operating characteristics of MCB in the power system of EMU powered by AC 25kV. The MCB is installed on the roof of the EMU vehicle and it performs on and off operations in poor environments conditions depending on the external environment, such as vibration and temperature changes due to operation. In the Shinbundang-Line driverless EMU vehicle system, as MCB’s operation failures occurred at outdoor temperature range of –1℃~ -11℃. It is analyzed the operate characteristic and the hypothesis theory of operation failure was established. It is verified experimentally and an applicable system is proposed that can operate smoothly under service environment condition. Finally, the results of the verification were applied to the train and the results of the proposed system were verified through long-term and follow-up observation.

Analysis of energy characteristics of absorption water-ammonia refrigeration machines in the waste heat recovery systems of gas turbine installations on gas main pipelines

One of the promising ways to reduce operating losses in main gas pipelines is pre-cooling of compressed gas using heat-using absorption water-ammonia refrigeration machines (AWRM), which utilize the waste heat of the exhaust products of the combustion of gas pumping units. The object of research is the energy characteristics of the AWRM in a wide range of operating parameters (outdoor temperatures), which are currently not studied. A methodology for modeling AWRM modes is developed, analytical studies are conducted and the results are obtained in a wide range of outdoor temperatures. The study is conducted using theoretical analysis of AWRM cycles in a wide range of outdoor temperatures and temperatures of the cooling object. The analysis of the calculation results showed that in the range of design parameters there is a maximum energy efficiency AWRM. The most obvious is the presence of a maximum for operating conditions at cooling medium temperatures of 20…32 °С and low temperatures of the cooling object (minus 25 °С). As the temperature of the cooling object decreases, the maximum energy efficiency shifts to the region of high temperatures of the heating medium, and its numerical values decrease. At heating source temperatures from 90 °С to 130 °С, the electric power of the circulation pump has a maximum value. Subsequently, with an increase in the temperature of the heating source, its asymptotic decrease and slow decrease are observed. In this case, the greatest changes occur at elevated temperatures of the cooling medium (32 °С). The simulation results allow to determine the most energy-efficient operating modes of the AWRM with various sources of thermal energy (temperatures from 90 to 160 °С) and to develop cooling systems for a wide temperature range (minus 30…15 °С). To achieve such optimal conditions, an appropriate combination of the composition of the working fluid and the temperature of the heating source is necessary.

Exergy Evaluation of a Heat Supply System with Vapor Compression Heat Pumps

The vapor compression heat pumps are very popular solutions regarding heat supply systems of modern, low energy buildings. It is partly due to the fact that they are treated as a sustainable heat supply. The question arises: Can a vapor compression heat pump be treated as a sustainable heat supply? To answer this question; the exergy model of a heat pump system operation has been proposed. The proposed model has been employed for evaluation of exergy efficiency of an existing heat supply system equipped with two heat pumps installed in an educational building located on the campus of Poznan University of Technology, Poznan, Poland. The analysis shows that the system exergy efficiency decreases with an increase in outdoor temperature and its values are in the range of 10.9% to 42.0%. The primary exergy efficiency, which considers the conversion of fossil fuel into electricity, is on average 3.2 times lower than the system exergy efficiency for the outdoor temperature range of −9 °C to 11 °C. The performed analysis allowed for the identification of a set of solutions that may increase the exergy and primary exergy efficiency of the system. The first solution is to cover a part of the electricity demand by a renewable energy source. The second proposition is to apply a low-temperature emission system for heating. The third idea is to apply a district heating network as the heat supply instead of the heat pump. The conclusion is that the exergy performance of systems with heat pumps is rather poor because they generate low-quality heat from high-quality electricity. The best way to improve the primary exergy efficiency of a heat pump system is to power the system by electricity generated from a renewable energy source.

Internal moisture excess of residential buildings in Finland

In Finland, the indoor air conditions of 171 single-family buildings and 49 apartments in multi-family buildings have been studied in large research projects in collaboration with Tampere University of Technology and Helsinki University of Technology. This article deals with the results of moisture excess studied in these single-family buildings and apartments. Continuous field measurements up to 28 months enable to include two consecutive heating seasons in the analysis of the internal moisture excess. The higher 10% critical level during the cold period (Te ≤ 5°C) was between 3.4 and 4.9 g/m3 in Finnish heavyweight and lightweight single-family buildings and between 2.4 and 3.6 g/m3 in apartments of multi-family buildings. During the warm period (Te ≥ 15°C), the corresponding values were between 0.3 and 2.6 g/m3 for single-family buildings and 0.5 and 1.5 g/m3 for apartments. The number of occupants and the airtightness of different groups of external wall did not have influence on the average values of moisture excess. Slightly better ventilation air change rates were measured in apartments of multi-family buildings, where also the air change rates from supply–exhaust ventilation systems generally fulfilled the Finnish guideline value. The design values of moisture classes in EN ISO 13788:2012 were found difficult to apply for Finnish residential buildings. The upper limit value of humidity class 2 of EN ISO 13788:2012 is suitable for apartments in Finnish multi-family buildings, but too low for Finnish lightweight and heavyweight single-family buildings. Applying the design values of Finnish guidelines would be justified for the studied buildings almost at the full range of outdoor temperatures.

Construction and Performance of a Self-Contained, Temperature-Controlled Heat Source (Electronic Chicken) to Quantify Thermal Load during Live Haul of Broilers

Abstract. Strategies for quantifying heat loss of broilers on live-haul trailers would be beneficial, particularly under conditions of environmental extremes. We have developed an electronic chicken (a self-contained, temperature-controlled heat source) to simulate the sensible heat loss of a live broiler during the transit and holding periods in commercial live-haul trips. The simulated electronic chicken is an aluminum box, having surface area equivalent to a 2.3 to 2.8 kg broiler chicken (0.13 m2), with a thermostatically controlled power source to maintain the internal temperature at 41°C (typical broiler core body temperature). Different cover materials were tested to identify an appropriate cover that resulted in measured values of electronic chicken heat production being similar to published values of sensible heat production for broilers. A double layer of fleece fabric provided a reasonable match. The sensible heat loss of the electronic chickens exhibited positive correlation with exposed wind, and a positive correlation with temperature gradient between internal and external environment. Wetting the fabric cover of electronic chickens only slightly increased heat loss as compared to the dry fabric cover. Wet fabric cover experienced lower heat loss than that expected from the wetted surface of a live chicken, therefore heat loss under the wet scenario would be underestimated. Electronic chickens were installed in modules on trailers with live chickens during commercial live-haul process under various environmental conditions and different management practices. Measured heat losses from electronic chickens were in the range of 8.2 to 20.3 W with outside temperature of -17°C to 3.0°C in winter, and 4.5 to 6.7 W with 28°C to 34°C in summer. Based on literature-reported sensible heat loss under thermoneutrality, it was determined that the measured air temperature inside the live-haul modules on the trailer in the range of 11°C to 25.1°C during transit (outdoor temperature range of 1.7°C to 22.2°C) and 5.3°C to 21.7°C during holding (outdoor temperature range of -9.1°C to 19.8°C) would allow the live chickens to regulate heat by their metabolism and stay comfortable. For the holding period, the winter trips were mostly in the zone of thermal comfort. In summers, hyperthermic conditions were possible during transit, although additional cooling due to surface wetting of birds as a result of misting (on the farm prior to beginning the transit) could have been beneficial but not detectable by electronic chickens. The electronic chickens can be used effectively as a model to evaluate and identify conditions that cause thermal stress conditions during live-haul conditions and to design systems and strategies to alleviate that stress. Keywords: Broiler transport, Physiological stress, Thermal micro-environment, Thermoneutral zone.

Energy savings from temperature setpoints and deadband: Quantifying the influence of building and system properties on savings

This paper provides a systematic approach for quantifying the influence of building size, construction category, climate, occupancy schedule, setpoint, and deadband on HVAC energy consumption in office buildings. Simulating the DOE reference office buildings of three sizes and three construction categories in all United States climate zones, using the EnergyPlus, we conducted several N-way ANOVA analyses to study the interrelationships between setpoints, deadbands and several building related and environment related factors. In summary, daily optimal deadband selection of 0, 1, 2, 4, 5, and 6K would result in an average energy savings of −70.0%, −34.9%, −13.7%, 9.6%, 16.4%, and 21.2%, respectively, compared to baseline deadline of 3K. Selecting the daily optimal setpoint in the range of 22.5±1°C, 22.5±2°C, and 22.5±3°C would result in an average savings of 7.5%, 12.7%, and 16.4%, respectively, compared to the baseline setpoint of 22.5°C. Additionally, we found that when the outdoor temperature is within −20 to 30°C, the optimal setpoint depends on the building size. We also observed a range of outdoor temperatures (e.g., 9–14°C for small buildings and 8–11°C for medium buildings) where the setpoint selection would only slightly influence the energy consumption. However, the choice of setpoints becomes very influential (up to 30% of energy savings) where the outdoor temperatures are slightly outside the mentioned ranges on either direction. The potential savings from selecting daily optimal setpoints in the range of 22.5±3°C in different climates and for small, medium and large office buildings, would lead to 10.09–37.03%, 11.43–21.01%, and 6.78–11.34% savings, respectively, depending on the climate.

Field studies of thermal comfort across multiple climate zones for the subcontinent: India Model for Adaptive Comfort (IMAC)

India is witnessing unprecedented growth trends in building construction, particularly office spaces. Indian offices are designed to operate at 22.5 ± 1 °C all year round to meet the stringent “Class A” specifications outlined by international standards in the absence of an India-specific comfort standard. This paper proposes an India Model for Adaptive Comfort – IMAC – based on the field surveys administered in 16 buildings in three seasons and five cities, representative of five Indian climate zones. A total of 6330 responses were gathered from naturally ventilated, mixed mode and air-conditioned office buildings using instantaneous thermal comfort surveys.Occupants in naturally ventilated Indian offices were found to be more adaptive than the prevailing ASHRAE and EN models would suggest. According to the IMAC model, neutral temperature in naturally ventilated buildings varies from 19.6 to 28.5 °C for 30-day outdoor running mean air temperatures ranging from 12.5 to 31 °C. This is the first instance where a study proposes a single adaptive model for mixed mode buildings asserting its validity for both naturally ventilated and air-conditioned modes of operation in the building, with neutral temperature varying from 21.5 to 28.7 °C for 13–38.5 °C range of outdoor temperatures. For air-conditioned buildings, Fanger's static PMV model was found to consistently over-predict the sensation on the warmer side of the 7-point sensation scale.

Numerical investigation on integrated system of mechanical refrigeration and thermosyphon for free cooling of data centers

The cooling energy consumption of data centers is increasing rapidly and free cooling attracts growing concern. To achieve the independent running of free cooling system all the year round, integrated system of mechanical refrigeration and thermosyphon (ISMT) is an ideal method. In this study, a distributed-parameter simulation model of an ISMT is built and validated by experimental data. The simulation results show that for thermosyphon mode, the cooling capacity increases with increasing air flow rate, temperature difference and pipe diameter, while decreases with increasing pipe length. For refrigeration mode, decreasing outdoor air temperature or increasing indoor air flow rate will improve the cooling capacity and reduce the input power of the compressor. For dual mode, applicable outdoor temperature range and indoor air flow rate range exist and the cooling capacity drops below that of refrigeration mode beyond these ranges. The critical values are 19 °C and 0.5 m3 s−1, respectively.