Air Temperature Control Research Articles

Hydrograph apportionment of the Chandra River draining from a semi-arid region of the Upper Indus Basin, western Himalaya.

Melting of snow and glaciers from the high-altitude Himalayan region is a significant water source to the major Himalayan rivers, especially in the upper Indus Basin (UIB), which contributes up to 70% of river discharge. Considering Indus Basin as a largest irrigation system dependent on snow and glacier melt runoff, it is imperative to study the rivers' current status and water budget. In this study we have performed a tracer-based hydrograph separation to quantify the contribution of seasonal snow, glacier melt, and groundwater to the Chandra River draining from a semi-arid region of the upper Indus basin, western Himalaya. Our study revealed a negligible control of summer (May-September 2017) precipitation and significant control of summer air temperature (May-September 2017) and winter precipitation over the Chandra River discharge, with 1°C rise in air temperature leading to 22 m3s-1 (15% of mean) increase in the river discharge (R2=0.85; n=541; p<0.001). The hydrograph separation of the Chandra River suggests groundwater (38.3±5.6%; 96.8 m3s-1) as a significant source to the river runoff, followed by a direct contribution from glacier melt (30.9±9%; 88.2 m3s-1) and seasonal snowmelt (30.6±5.7%; 84.2 m3s-1), respectively, with negligible contribution from rainfall. Although groundwater is a significant contributor to the river runoff, the infiltration of seasonal snowmelt (54%) and glacier melt (46%) mostly contributed to the groundwater recharge. Present study establishes a linkage between seasonal snowmelt, glacier melt, groundwater, and the river runoff and would be useful to better model and predicts the future changes in the water resources of the upper Indus Basin.

Dynamic model and response characteristics of liquid desiccant air-conditioning system driven by heat pump

The liquid desiccant air-conditioning system is considered as an energy-efficient alternative to the vapor compression system. The dynamic response characteristics of the system under variable cooling load play an important role in the air temperature and humidity control performance of the system. However, the dynamic response characteristics have not been fully revealed in previous studies. Thus, a dynamic model for a heat pump driven liquid desiccant air-conditioning (HPLDAC) system is established to investigate the dynamic response characteristics of the system in this study. Subsequently, experiments were conducted to validate the accuracy of the dynamic model. The simulation results show a good agreement with the experimental data. The simulation results reveal that evaporating water from the solution is a time-consuming process, compared to adding water to the solution. It spends a long time for the HPLDAC system to decrease the high relative humidity of supply air to a low value, which limits the air temperature and humidity control performance of the system. The upper band for the water replenishing value opening (Δφup) is a crucial parameter to improve the limitation. When Δφup decreases from 1.0% to 0.25%, the time consumed to reduce the supply air relative humidity to the new lower set value can be saved by 30.6%.

Radiative cooling for dew condensation

We describe a radiative cooling chamber which reproduces in the laboratory radiative cooling and subsequent dew formation. Based on radiative exchange with a cold source (at a temperature of nearly -80 °C), which acts as a cold black body, cooling power of at least 50 W.m-2 is achieved. Radiative exchange is quantitively estimated. This original device permits to study under controlled air temperature and humidity the formation of dew on any system (material, biological) for which contact cooling is inefficient, and in particular investigate the influence of radiative and wetting surface properties on dew yield. It is applicable to the study of dew itself and its effects on plants and small animals, as well as dew atmospheric chemistry, and more generally of any natural radiative cooling application.

The use of solar energy in air temperature control systems in industrial premises

It has been proposed to use absorption chillers that use solar energy for food processing enterprises. The simulation of the system in the Matlab environment showed that it is necessary to install digital controllers in temperature control systems that ensure the maintenance of the specified accuracy.

Key performance indicators for the evaluation of building indoor air temperature control in a context of demand side management: An extensive analysis for Romania

Besides being the main consumer of energy, buildings can be smart energy hubs offering demand side flexibility for the grid. The main loads in buildings are heating and cooling and they have the advantage to be flexible if controlled in a smart way. There are plenty of ways in which controllers can act for increasing the demand side energy flexibility of buildings and different approaches in quantifying and assessing it.This study uses a set of three existing key performance indicators to make a qualitative assessment on how the heating and cooling energy control is impacting indoor thermal comfort, the costs with energy and the self-consumption of the locally produced energy for a typical household located in different geographical conditions in Romania, under an electricity market design with a demand response program. The selected metrics are adapted for this analysis to allow a quick qualitative evaluation on how the building and its systems can reach the maximum achievable potential in terms of comfort, costs, and self-consumption. This approach can be applied both at design and operational phase. The results show that the participation in a demand response program does not influence negatively the indoor thermal comfort if constraints are imposed on these parameters, that the geography does not have a relevant impact upon the costs if a control technique dedicated for the participation in the demand response program is implemented and the participation in a demand response program does not influence the self-consumption.

Overall performance of steam system used in garment industries in Bangladesh: a case study–based approach

The fabric or garments production activities starting from raw material preparation to the finishing process are energy-intensive. Steam generation and distribution system is part of all the major processes involved here. Therefore, this study aims to assess the overall performance of the steam system used in the textile or garment industry in Bangladesh. The quantity of heat loss through different sources both at steam generation and distribution unit was computed. The amount of in-process heat energy consumption was also determined. Current practices in steam system management were investigated, and opportunity for improvement was addressed. Finally, the genetic algorithm approach was used to optimize the process parameters of steam generation unit thermodynamically. The average efficiency of the steam generation units used in the fifteen studied factories was found 76%. The dyeing and ironing processes were found as the most heat energy–intensive process. Among the sources of heat losses, maximum loss was found occurring through the dry flue gas during steam generation. At distribution unit, most heat is lost through the steam line and in-process distribution. Based on the analysis, daily 694 GJ heat passes away through a steam system resulting in 13 tons and 31 tons of fuel wastage and greenhouse gas emission, respectively. Considering the occurring losses, the remedial measures were focused on excess air and stack temperature control, improvement in boiler operating condition, steam leakage and trap maintenance, insulation enhancement, etc. Moreover, by optimizing the thermodynamic process parameters, it is possible to increase energy efficiency by almost 3.0%.

Mathematical model and energy efficiency analysis of a vacuum-based liquid desiccant regenerator

Liquid desiccant air conditioning (LDAC) has been considered as a promising solution for efficient air temperature and humidity control in air conditioning fields. However, the high regeneration temperature of desiccant solution impedes its spread and application. In this study, a vacuum-based liquid desiccant regenerator (VLDR) for desiccant solution regeneration in LDAC driven by low-grade energy is studied, meanwhile, the mathematical model considering the variation of heat transfer coefficient under different operating conditions is developed to analyze the system performance and energy efficiency. After the model is validated by the experimental data, the regeneration performance and energy efficiency analysis of the VLDR system is simulated and investigated. Simulation results show that hot water temperature, flowrate are the variables that affect the performance of the generator, and the performance of the condenser is influenced by cooling water temperature and flowrate. Opposite influences for vacuum pressure are found on the performances of generator and condenser, therefore the hot water temperature, vacuum pressure, and cooling water temperature should be designed properly to provide the required regeneration capacity with the pressure balance maintained. Moreover, energy efficiency is analyzed by comparing the ratio of water vapor generation rate to the total electricity consumption of the VLDR under different temperatures and vacuum pressures.

Airborne Fungi in Library Environment and Human Health Risks

Objetive: This review aims to approach the impact that airborne fungi have in collections, mainly in libraries, and also their impact in the health of the people who works and visiting there. Methodology: The search was made with the most recent papers, with free access in online databases: Pubmed (National Library of Medicine and the National Institutes), Lilacs (Latin-American and Caribbean Literature in Health Science, acronym in Spanish) and Scielo (Scientific Electronic Library Online), by using key words related with the proposed theme. Results: Libraries have substrates and residuals that allow the presence and proliferation of airborne fungi. These fungi are biodeteriorators that attack the collections but also can cause respiratory diseases, mycoses, or even systemic diseases. The most common genera are Aspergillus, Penicillium, Cladosporium, Alternaria, Acremonium and Fusarium. These fungi have asexual reproduction by producing tiny dry spores that can remain viable by long periods on the air and can also be transported on it. Preserve collections demands control of air temperature and humidity, to inhibit the airborne fungi proliferation and thus, decreasing the risks to human health. Conclusion: The knowledge about airborne fungi as contaminants in libraries environment it is of utmost importance for the development of preventive actions for preservation of the collections and also for the health of people who works in or visit them.

Transient Energy Models of Housing Facilities Operation

Buildings are the main consumer of energy resources in the total energy balance of the countries in Central and Eastern Europe, the main energy consumption is allocated for heating. Efficient use of energy resources for heating needs to a large extent depends on the efficiency of regulation of heating systems. In the article, dynamic mathematical models of a two-room typical apartment in Ukraine, built in 2016, were developed in Matlab and EnergyPlus software environment. The simulations were carried out using IWEC hourly climate data for the city of Kyiv. The results of simulations of thermal energy consumption in Matlab are characterized by a larger range of fluctuations of the heating system load, which is typical for the real operating conditions of the system with the controller of ON/OFF type. In EnergyPlus it is assumed that the gas boiler operates continuously in the ON mode. In the research, the change of load on the apartment heating system was studied at different numbers and locations of air temperature control sensors installation, according to which the controller of the autonomous gas boiler operates.

The Combined Conditions of Photoperiod, Light Intensity, and Air Temperature Control the Growth and Development of Tomato and Red Pepper Seedlings in a Closed Transplant Production System

Understanding environmental factors is essential to maximizing the biomass production of plants. There have been many studies on the effects of the photosynthetic photon flux (PPF), photoperiod and air temperature as separate factors affecting plants, including under a closed transplant production system (CTPS). However, few studies have investigated the combined effects of these factors on plant growth. Germinated tomato and red pepper seedlings were transferred to three different photoperiods with five different photosynthetic photon fluxes (PPFs) at an air temperature of 25/20 °C to investigate plant growth under a different daily light integral (DLI). Three different air temperatures, 23/20, 25/20, and 27/20 °C (photo/dark periods), with five different PPFs were used to examine plant growth under different DIFs (difference between the day and night temperature). Increasing the DLI from 4.32 to 21.60 mol·m−2·d−1, either by increasing the photoperiod or PPF, improved the growth of seedlings in both cultivars. However, when comparing treatments that provided the same DLI, tomato seedlings had s significantly higher growth when grown under longer photoperiods and s lower PPF. Even in higher DLI conditions, reduced growth due to higher PPF indicated that excessive light energy was a limiting factor. At 23 and 25 °C, tomato seedlings showed similar correlation curves between growth and PPF. However, at the higher temperature of 27 °C, while the slope of the curve at low PPFs was similar to that of the curves at lower temperatures, the slope at high PPFs was flatter. On the other hand, red pepper seedlings displayed the same correlation curve between growth and PPF at all tested temperatures, and red pepper plants accumulated more dry weight even at higher temperatures. These results suggested that the combination effect was more useful to observe these overall tendencies, especially in reacting to a second factor. This will provide us with more information and a deeper understanding of plant characteristics and how they will behave under changing environments.

Personal Atmosphere: Estimation of Air Conditioner Parameters for Personalizing Thermal Comfort

Air conditioners enable a comfortable environment for people in a variety of scenarios. However, in the case of a room with multiple people, the specific comfort for a particular person is highly dependent on their clothes, metabolism, preference, and so on, and the ideal conditions for each person in a room can conflict with each other. An ideal way to resolve these kinds of conflicts is an intelligent air conditioning system that can independently control air temperature and flow at different areas in a room and then produce thermal comfort for multiple users, which we define as the personal preference of air flow and temperature. In this paper, we propose Personal Atmosphere, a machine learning based method to obtain parameters of air conditioners which generate non-uniform distributions of air temperature and flow in a room. In this method, two dimensional air-temperature and -flow distributions in a room are used as input to a machine learning model. These inputs can be considered a summary of each user’s preference. Then the model outputs a parameter set for air conditioners in a given room. We utilized ResNet-50 as the model and generated a data set of air temperature and flow distributions using computational fluid dynamics (CFD) software. We then conducted evaluations with two rooms that have two and four air conditioners under the ceiling. We then confirmed that the estimated parameters of the air conditioners can generate air temperature and flow distributions close to those required in simulation. We also evaluated the performance of a ResNet-50 with fine tuning. This result shows that its learning time is significantly decreased, but performance is also decreased.

STUDI PENANGANAN HASIL TANGKAPAN PURSE SEINE DI KM BINA MAJU KOTA SIBOLGA

Penanganan hasil tangkapan merupakan salah satu faktor yang mempengaruhi kesegaran serta kualitas ikan hasil tangkapan. Upaya yang dilakukan pemerintah dalam menjaga mutu produk perikanan adalah dengan mengeluarkan KEPMEN-KP 52A/2013 tentang Persyaratan Jaminan Mutu dan Keamanan Hasil Perikanan pada Proses Produksi, Pengolahan, dan Distribusi. Keberpihakan pemerintah dengan mengeluarkan KEPMEN-KP 52A/2013 diharapkan dapat menghasilkan produk perikanan yang baik, aman, dan sehat. Tujuan dari penelitian ini adalah mengetahui kegiatan penanganan hasil tangkapan dan mengetahui kesesuaian kegiatan penanganan di KM Bina Maju dengan KEPMEN KP 52A/2013. Metode penelitian yang digunakan adalah studi kasus. Objek atau lokasi kegiatan penanganan ikan di KM Bina Maju yang telah menerapkan prinsip 3C1Q Clean, Carefull, Cold, dan Quick. Kesesuaian kegiatan penanganan di atas KM Bina Maju dengan KEPMEN KP 52A/2013, adalah ketersediaan palka yang digunakan untuk penyimpanan hasil tangkapan yang terpisah dari ruang mesin dan ruang ABK. Hanya saja dalam palka belum dilengkapi dengan mesin pendingin air laut dan pengatur otomatis suhu udara. Kesesuaian SDM dengan KEPMEN KP 52A/2013 adalah kondisi ABK yang sehat, tidak merokok, dan tidak meludah di area penyimpanan. Ketidaksesuaiannya adalah kurangnya kesadaran dalam penggunaan pakaian kerja dan kegiatan mencuci tangan sebelum kegiatan penanganan hasil tangkapan.

Rancang Bangun Farming Box Dengan Pengaturan Suhu Menggunakan Fuzzy Logic Controller

Implementation of control systems has been carried out in many fields of science. One of it applications is in the agriculture fields. In this research we implemented a control system on farming in a box. Farming in a box is a system that uses old shipping containers for the purpose of growing plants in any environment. Inside shipping containers is fully assembled hydroponic pipe with air temperature control. In this research was built a little farming box from acryclic to imitate a shipping container. Main focus of this research is design an air temperature control using fuzzy logic controller. Fuzzy logic controller was choosen because many existing farming box use on off controller. In some application, fuzzy logic controller has better performance than on off controller. Farming box temperature is controlled by blowing cool air using an electric fan. In this case, cool air is produced by cold side of peltier. Electric fan speed is controlled by pulse width modulation signal (PWM) that generated from microcontroller. Air temperature data feedback is obtained from DHT 11 sensor that installed in a acrylic box. Sensor is physically connected with microcontroller and Fuzzy logic controller is embedded in microcontroller as an algorithm. Fuzzy logic controller was design with error temperature and error difference as an input, and duty cycle of PWM signal as output. Fuzzy logic controller system performs to reduce the temperature from 31,6 ° C to set poin 28° C in 71 seconds. Steady state error obtained by 1.28% and better than uncontrolled system that obtain steady state error 7,14%.

Feasibility study on temperature control with phase change material in intensive heat-releasing space during emergency power failure: A case analysis of information system room

Phase change material (PCM) is widely used to control temperature because of its easy control, and independent work even without external power supply. However, few studies focus on temperature control via a PCM cooling system without auxiliary facilities, in an intensive heat-releasing space during emergency power failure. This study takes an information system room with an emergency power failure as the research object. A cooling system implementing PCM plates is proposed and its feasibility is analyzed. A mathematical heat transfer model, which considers the air, heat source, phase change cooling devices, and the enclosure structure of room, is established. The performance of the PCM and air temperature are analyzed, and the effects of the melting temperature, latent heat, thermal conductivity, and size of the PCM plates are systematically investigated. Analysis results indicate that: (i) Under the condition of parameter optimization, the air temperature is 32.10 °C at 9 h. Therefore, the cooling system utilizing the PCM plates can effectively maintain the air temperature of the information system room below 35 °C within 9 h. Until 16 h, the air temperature remains below 35 °C. (ii) Increasing the aspect ratio of PCM plates and decreasing PCM latent heat have the similar effect on the air temperature control. Additionally, the two parameters are related to the surface area of the PCM plates. (iii) The lower the melting temperature of the PCM, the better the air temperature can be controlled. For the conditions considered in this study, the appropriate melting temperature is approximately 25 °C. (iv) As thermal conductivity increases, air temperature reduces, and fluctuation of the PCM heat flow significantly decreases. However, as the thermal conductivity approaches 1 W/(m·K), further increases in the thermal conductivity have no marked impact on air temperature control.

Optimisation of Control Input Allocation Maps for Electric Vehicle Heat Pump-based Cabin Heating Systems

The heating, ventilation and air conditioning (HVAC) system negatively affects the electric vehicle (EV) driving range, especially under cold ambient conditions. Modern HVAC systems based on the vapour-compression cycle can be rearranged to operate in the heat pump mode to improve the overall system efficiency compared to conventional electrical/resistive heaters. Since such an HVAC system is typically equipped with multiple actuators (compressor, pumps, fans, valves), with the majority of them being controlled in open loop, an optimisation-based control input allocation is necessary to achieve the highest efficiency. This paper presents a genetic algorithm optimisation-based HVAC control input allocation method, which utilises a multi-physical HVAC system model implemented in Dymola/Modelica. The considered control inputs include the cabin inlet air temperature reference, blower and radiator fan air mass flows and secondary coolant loop pumps’ speeds. The optimal allocation is subject to specified, target cabin air temperatures and heating power. Additional constraints include actuator hardware limits and safety functions, such as maintaining the superheat temperature at its reference level. The optimisation objective is to maximise the system efficiency defined by the coefficient of performance (COP). The optimised allocation maps are fitted by proper mathematical functions to facilitate the control strategy implementation and calibration. The overall control strategy consists of superimposed cabin air temperature controller that commands heating power, control input allocation functions, and low-level controllers that ensure cabin inlet air and superheat temperature regulation. The control system performance is verified through Dymola simulations for the heat pump mode in a heat-up scenario. Control input allocation map optimisation results are presented for air-conditioning (A/C) mode, as well.

Creation of Dynamic Model for Optimization of the Temperature Control Loop in the Air Conditioning System of an Aircraft

The temperature control loop of the actuating air following the heat exchanger is considered. The control loop consists of a heat exchanger, adjustable air intake, circulation fan, temperature sensor, and temperature controller. A dynamic model of the control loop that takes into account the automatic control system is created. Transient processes that arise in the control loop as a consequence of variations of the altitude of the aircraft are considered. Results of the variation in the actuating air temperature at a temperature control point are obtained. Partial optimization of the coefficients of the controller is performed. Optimal coefficients of the controller are selected.

Modelling of Natural Convective Heating of a Standard Wet Brick for Oven Energy Consumption Tests

The environmental impact of buildings is directly influenced by low-efficiency appliances like electric ovens. Their energy class is estimated through a test prescribed by the EN 60350 European standard, where a wet clay brick is heated under set conditions and the energy consumption is measured; throughout the test, particular attention is devoted to the control of air temperature. In this work, a transient model of the oven suitable for control design was realized including the heat and mass transfer within the brick. A lumped-parameter approach was used to ensure good predictive properties and low computational cost. The dynamics of the cavity air and the Pt500, which is used in normal operation to maintain the desired set point, was also included in the model. Model parameters were determined through an optimization procedure based on the experimental data collected during energy consumption tests with the oven in natural convective heating mode. The model was then validated. Good results were obtained in the prediction of both temperature and heating time.

Enhancing Historic Building Performance with the Use of Fuzzy Inference System to Control the Electric Cooling System

In recent years, the interest in properly conditioning the indoor environment of historic buildings has increased significantly. However, maintaining a suitable environment for building and artwork preservation while keeping comfortable conditions for occupants is a very challenging and multi-layered job that might require a considerable increase in energy consumption. Most historic structures use traditional on/off heating, ventilation, and air conditioning (HVAC) system controllers with predetermined setpoints. However, these controllers neglect the building sensitivity to occupancy and relative humidity changes. Thus, sophisticated controllers are needed to enhance historic building performance to reduce electric energy consumption and increase sustainability while maintaining the building historic values. This study presents an electric cooling air controller based on a fuzzy inference system (FIS) model to, simultaneously, control air temperature and relative humidity, taking into account building occupancy patterns. The FIS numerically expresses variables via predetermined fuzzy sets and their correlation via 27 fuzzy rules. This intelligent model is compared to the typical thermostat on/off baseline control to evaluate conditions of cooling supply during cooling season. The comparative analysis shows a FIS controller enhancing building performance by improving thermal comfort and optimizing indoor environmental conditions for building and artwork preservation, while reducing the HVAC operation time by 5.7%.

Influence of intake air temperature control on characteristics of a Homogeneous Charge Compression Ignition engine for hydrogen-enriched kerosene-dimethyl ether usage

In this study, the high-speed of 2000 rpm and low-speed of 1000 rpm behaviors on the HCCI test engine at full load were examined experimentally by controlling the intake air temperature. The tests were carried out at 0.90 equivalence ratio for hydrogen-enriched kerosene-dimethyl ether mixture. In order to expand the usage of HCCI engines in daily life, their problems encountered at high loads and high speeds need to be solved. The main reason of these problems is the control of the start of combustion since there is no external combustion system in HCCI engines.The experimental results show that the intake air temperature directly affects engine performance and emissions. The intake air temperature control was led to shorter flame development time and better combustion stability. The in-cylinder pressure at 1000 rpm for 373 K is overall 6.82% and 4.07% higher than the 273 K and 298 K. The average heat release rate curve trends at 1000 rpm are overall 45.68% higher than 2000 rpm. The brake specific fuel consumption for 2000 rpm is about 5.29% higher than 1000 rpm. The differences between the two NOx trends are 35.4% maximum and 11.03% minimum for 1000 rpm and 2000 rpm. At high engine speed, the HC formation drops linearly from 488 ppm to 339 ppm with increasing air temperature. Also, the soot formation decreased with a slope of 1.58 times higher than 1000 rpm. Overall, the increase in intake air temperature at the tests positively affected in-cylinder pressure, CO, HC and soot.

Impacts of Tree Canopy Cover on Microclimate and Human Thermal Comfort in a Shallow Street Canyon in Wuhan, China

Increasing the number of street trees can be a promising method to reduce impacts of climate change currently impacting urban public health. However, the quantitative relationships between tree canopy cover and thermal comfort remains unclear, particularly in areas with high temperature and high humidity. This study aims to provide a better understanding of the effects of different degrees of tree canopy cover on human thermal comfort in shallow street canyons in a high temperature, high humidity area of China. Microclimatic measurements and qualitative surveys were conducted on sunny summer days in a shallow street canyon in Wuhan. The results suggest that microclimate benefits are greater for areas with a high-percentage tree canopy cover compared to medium- and low-percentage tree canopy cover—especially at noon. In streets with a high-percentage tree canopy cover, afternoon air temperatures and mean radiant temperatures can be reduced by up to 3.3 °C and 13.9 °C, respectively, compared to a similar street with no tree shade. The thermal sensation prediction formula is proposed and the relationship between human thermal sensation and microclimate factors is established. Blocking solar radiation and increasing wind speed are more feasible than controlling air temperature and humidity as ways to improve human thermal comfort.