Room Temperature In Air Research Articles

Investigation of the cooling performance and thermal comfort for 4-way cassette air conditioner with swinging motion of vanes

A numerical simulation was carried out to investigate the cooling performance and thermal comfort of a 4-way cassette air conditioner when its vanes are positioned at constant angles of 30°, 40°, 50° and 60° and swinging with a constant angular velocity. The indoor airflow characteristics and thermal comfort were evaluated. The average room temperature variation with respect to time have a good agreement with the measured data with a maximum relative error of 2 %. The average room air temperature variation according to time shows that the case of swinging vane is increased by 5.9 %, compared to the case of fixed vane angle of 60°, due to the enhancement of heat transfer by the swinging motion of discharged airflow. Moreover, the flapping discharged airflow resulting from the swinging motion makes occupants feel thermally more comfortable, based on thermal comfort indices.

Passive air cooling system and solar water heater with Phase Change Material for low energy buildings in hot arid climate

Solar energy is considered alternative crucial to fulfilling the increasing of energy requirements. Passive cooling systems are considered alternatives to mechanical ventilation systems. In this work, a highlight for a solar chimney with water heater and Phase Change Material is applied as a passive solar technique for cooling building integrated with short wind tower for low energy building in the hot arid climate. This paper aims to investigate the performance of new passive air condition system with the solar chimney and solar water heater as a full system for cooling air and heating water to be applied during day and night time based on the improvement of the solar chimney in Assiut climate, Egypt. Measurements, for air temperatures and surface temperature of the aluminium and air velocity inside the chimney, water temperature and room temperature were conducted with different solar radiations to evaluate the panel performance and room thermal comfort. The findings show a minimum airflow rate in the chimney after sunset equal to 0.69 kg/s to provide fresh cold air during a hot day with a water temperature equal 58 °C and 40 °C during 2 pm and after sunset respectively. Also, integration of solar chimney and PCM with cooling wind tower achieves a significant reduction for room air temperature between 8 and 4 k during day and night time respectively and the condition within the comfort range of Predicted Mean Vote (PMV) especially night time. The results provided information to integrate this new low energy compact passive air cooling and water heating system for the housing projects of the upper floor in a hot arid climate in Egypt.

Planar laser-induced fluorescence thermometry in moderate-temperature flow using OH from photo-dissociation of water vapor

Since planar laser-induced fluorescence (PLIF) temperature measurements in a combustion-flow field can only be performed in regions in which OH is abundant (i.e., the reaction and high-temperature burnout zones), this paper investigates the feasibility of using photolysis of dissolved water to generate additional OH in the low-temperature and non-reaction zones of the flow field. Multi-line fluorescence showed that the generated OH had reached thermal equilibrium within 50 ns after dissociation with a fitting temperature of 300 K in room-temperature air. To further verify the technical accuracy, averaged PLIF images from dissociated OH were calibrated and compared with thermocouple measurements in a heated-flow field, and the average deviation in the 423–823 K temperature range was less than 40 K, with a relative system error better than 5%. The results of this paper confirm the feasibility and accuracy of the photo-fragment PLIF (PF-PLIF) temperature measurement in a low-temperature flow field. This makes it an effective complement to traditional PLIF measurements, with great significance for analysis and model validation of combustion processes in low temperature.

Physicochemical properties of 1,3-dimethyl-2-imidazolinone−ZnCl2 solvated ionic liquid and its application in zinc electrodeposition

Zinc chloride (ZnCl 2 ) was dissolved in the 1,3-dimethyl-2-imidazolinone (DMI) solvent, and the metallic zinc coatings were obtained by electrodeposition in room-temperature ambient air. The conductivity ( σ ), viscosity ( η ), and density ( ρ ) of the DMI−ZnCl 2 solvated ionic liquid at various temperatures ( T ) were measured and fitted. Furthermore, cyclic voltammetry was used to study the electrochemical behavior of Zn(II) in the DMI−ZnCl 2 solvated ionic liquid, indicating that the reduction of Zn(II) on the tungsten electrode was a one-step two-electron transfer irreversible process. XRD and SEM−EDS analysis of the cathode product confirmed that the deposited coating was metallic zinc. Finally, the effects of deposition potential, temperature and duration on the morphology of zinc coatings were investigated. The results showed that a dense and uniform zinc coating was obtained by potentiostatic electro- deposition at −2 V (vs Pt) and 353 K for 1 h.

Environmental fatigue correction factor model for domestic nuclear-grade low-alloy steel

Low cycle fatigue behaviors of SA508-3 low-alloy steel were investigated in room-temperature air, high-temperature air and in light water reactor (LWR) water environments. The fatigue mean curve and design curve for the low-alloy steel are developed based on the fatigue data in room-temperature and high-temperature air. The environmental fatigue model for low-alloy steel is developed by the environmental fatigue correction factor (Fen) methodology based on the fatigue data in LWR water environments with the consideration of effects of strain rate, temperature, and dissolved oxygen concentration on the fatigue life.

Effect of movable insulation on performance of the Building integrated Semi-transparent Photovoltaic Thermal (BiSPVT) system for harsh cold climatic conditions: a case study

ABSTRACT Semi-transparent photovoltaic modules are integrated with the building’s rooftop with the provision of movable insulation during off-sunshine hours to reduce the heat losses from room to the ambient. A significant rise in room air temperature of about 6°C at desired hours for cold climatic conditions of Srinagar, India was noted in this study. Also, a metallic drum filled with water has been placed inside the room to reduce the room temperature fluctuations, thus reducing the thermal load leveling. The study is also focused to analyse the simultaneous impact of natural ventilation, direct gain and daylight savings through the south-facing window, thus leading to daylight savings and reducing the dependency on artificial modes of illumination. The effect of water mass and packing factor has also been studied on electrical energy and daylight savings. Analytical expressions for water, metallic drum/tank, room, floor and solar cell temperatures have been derived.

Air temperature stratification when flowing between rooms

The article presents the regularities of the vertical change in the air temperature of a ventilated room for various purposes, where the excess of sensible heat dominates, in the first case, when there is no process of air flow through the opening in a common vertical fence between the rooms located in a row, or the second case, when a similar air flow is observed. In heat-stressed rooms, the general ventilation arrangement scheme provides for the removal of air from the upper volume of the room. To determine the required air exchange with point, two-zone or multi-zone mathematical models of a ventilated room, it is necessary to have a reliable apparatus for determining the gradient of the vertical air parameters change for a ventilated room. The reasonably determined value of the gradient of the air temperature change along the vertical of the ventilated room makes it possible to calculate the air flow between different volumes inside the ventilated room. Determination of the air temperature near the suction flare makes it possible to determine the required air exchange more reasonably. A method is given for calculating the distribution of air temperature in rooms with an excess of apparent heat over the height of the room in the first case, when there is no process of air flow through the opening in the common vertical fence between the rooms located in a row, or the second case, when a similar air flow is observed. This takes into account the height of the supply air distributors relative to the working (serviced) area. Reasonable determination of the air temperature at different points in the room with an excess of sensible heat allows a correct calculation of the required air exchange. The presented method for determining the gradient of air temperature stratification along the height of the room with air flow between adjacent rooms and without it contributes to the reasonable determination of the air temperature at the suction flame of the exhaust air distributor, which increases the reliability of calculating the required air exchange.

Copper(ii)-catalyzed protoboration of allenes in aqueous media and open air

A copper(ii)-catalyzed internal protoboration of monosubstituted allenes efficiently occurs in water at room temperature and open air to generate 1,1-disubstituted vinyl boronic acid derivatives.

Cooling Capacity and Energy Performance of Open-Type Ceiling Radiant Cooling Panel System with Air Circulators

Ceiling radiant cooling panel (CRCP) systems are being increasingly applied to commercial buildings due to their high thermal comfort level and energy efficiency. It is recommended that CRCP systems should be operated at a relatively high chilled water temperature to prevent condensation and save energy. However, even though a high chilled water temperature is effective for achieving condensation-free operation and high chiller efficiency, it can lead to insufficient cooling capacity. In this study, a method of enhancing the cooling capacity of CRCP systems was investigated through mock-up chamber tests. The open-type installation of CRCPs and the combination of air circulators were used to enhance the cooling capacity and energy performance of CRCP systems. Experimental results showed that compared to a conventional CRCP system, the cooling capacity of an open-type CRCP system with air circulators increased by up to 26.2%, and its cooling energy consumption decreased by up to 26.4%. Additionally, the open-type CRCP system with air circulators reduced the difference between the room air temperature and mean chilled water temperature. Thus, the proposed system can operate at a relatively high chilled water temperature, which is effective for reducing condensation risk and cooling energy consumption.

Indoor environment of nearly zero energy residential buildings with conventional air conditioning in hot-summer and cold-winter zone

• Explore the cooling demand of nearly zero energy residential buildings. • Indoor temperature variation and load characteristics under three air-conditioners. • Indoor environment under a newly proposed convective-radiation air conditioning. According to the few researches on Nearly zero energy residential buildings (NZERB) in hot-summer and cold-winter zone, although it could reduce the cooling load of buildings due to its high thermal insulation and air tightness, it still needed for certain cooling in summer. This paper studied indoor environment of NZERB under three kinds of air-conditioners (split-type air-conditioner, multi-line air-conditioner and ceiling radiant air-conditioner). Firstly, a simulation model of NZERB was established based on Nanjing, a typical city in hot-summer and cold-winter zone. Secondly, variation of indoor air temperature and building load characteristics with outdoor air temperature were studied. Thirdly, indoor environment and energy consumption under three selected conventional air-conditioners in summer were simulated. Finally, the discussion was given, and an air-conditioner combining with convective and radiant cooling were proposed. The results indicated that the air-conditioner needed to be turned on in NZERB in hot-summer and cold-winter zone due to the room air temperature in off-air condition ranged from 32 °C to 36 °C, which was higher than designed indoor environment temperature in summer, but the indoor environment of NZERB under three selected conventional air-conditioners could not meet the requirements of energy saving and comfort at the same time, and a proposed convective-radiant air-conditioner could be fast, stable, and energy saving. The findings can provide a reference for conducting active technology in NZERB.

A solar regenerated liquid desiccant evaporative cooling system for office building application in hot and humid climate

In this paper, we provide the thermal analysis and design methodology of a liquid desiccant assisted dew point indirect evaporative cooling system. The purpose of the system is to serve as an alternative for conventional vapour-compression based building air conditioning systems in providing satisfactory human thermal comfort conditions in the hot and humid climatic regions. The main features of the study are the following: i) novel incorporation of a forced parallel flow direct solar regenerator and a dew point indirect evaporative cooler within the same air conditioning unit; ii) detailed thermal modelling of each of the system components with fewer simplifying assumptions compared to earlier works; iii) large cooling capacity (~18.8 TR) under harsh climate; and, iv) a comprehensive year-round case study for system operation in a hot and humid location (Kolkata, India). Our thermal model is validated with a reference model study. The maximum room air temperature predicted by the current system for year-long analysis is 26.7 °C. The thermal COP of the system for diurnal operation in the most humid month of a calendar year (July) varied between 0.40 and 0.96. The cooling system can prevent overheating of the conditioned space, as specified by ASHRAE Standard 55–2017, throughout the year.

PoDIT: Portable Device for Indoor Temperature Stabilization: Concept and Theoretical Performance Assessment

This work introduces the concept of a new Portable Device for Indoor Temperature Stabilization (PoDIT), to be considered as a low-cost, quick and easy to implement remediation strategy when, for social, economic, or technical reasons, the improvement of the building envelope and/or the adoption of air conditioning are not possible. The main goal is to attenuate the maximum indoor temperature during summer and/or heat waves. The system, which is modular, consists of a certain mass of encaged phase change material (PCM) that stays indoors during the daytime and is transported to the outdoors (e.g., a balcony) during the night to discharge the heat accumulated during the daytime. Both natural convection and forced convection variants were considered. The results showed that, in the configurations and for the reference room and weather considered, the adopting 4 modules of the device can lead to reductions in the maximum room air temperature close to 3 °C, with natural convection. Adopting a fan to impose forced convection at the surfaces of the device can lead to temperature attenuations in excess of 4 °C, as it ensures full solid–liquid commuting and therefore optimal use of the PCM thermal storage capability.

The comparison of design airflow rates with dynamic and steady-state displacement models in varied dynamic conditions

A temperature-based method is usually applied in displacement ventilation (DV) design when overheating is the primary indoor climate concern. Different steady-state models have been developed and implemented to calculate airflow rate in rooms with DV. However, in practical applications, the performance of DV depends on potentially dynamic parameters, such as strength, type and location of heat gains and changing heat gain schedule. In addition, thermal mass affects dynamically changing room air temperature. The selected steady-state and dynamic models were validated with the experimental results of a lecture room and an orchestra rehearsal room. Among the presented models, dynamic DV model demonstrated a capability to take into account the combination of dynamic parameters in typical applications of DV. The design airflow rate is calculated for the case studies of dynamic DV design in the modelled lecture room in both dynamic and steady-state conditions. In dynamic conditions of heavy construction in 2–4 hours occupancy periods, the actual airflow rate required could be 50% lower than the airflow rate calculated with the steady-state models. The difference between steady-state and dynamic multi-nodal model is most significant with heavyweight construction and short occupancy period (17%–28%). In cases with light construction, the dynamic DV model provides roughly the same airflow rates for four-hour occupancy period than the Mund’s model calculates. The dynamic model can significantly decrease the design airflow rate of DV, which can result in a reduction of investment costs and electrical consumption of fans.

Comparison of the effects of symmetric and asymmetric heat load on indoor air quality and local thermal discomfort with diffuse ceiling ventilation

In this study, indoor air quality and thermal conditions were studied under laboratory conditions with the heat load that was located symmetrically or asymmetrically in the room. Diffuse ceiling ventilation (DCV) was adopted to provide cooling and outdoor air to the room. CO2 concentration, room air temperature and air speed were measured in the test chamber. This study gives insight of both thermal comfort and indoor air quality with different heat load levels and load distribution. The results show that the strength, distribution and the type of heat load have a significant influence on air distribution and thermal comfort. In all cases, the performance of the diffused ceiling ventilation was like fully mixed ventilation. The mean air temperature and speed increase with the heat load, as a result, also draught rate increases, which meant the heat load distribution has effect on local thermal discomfort.

A simulation study of radiant chilled ceiling with dedicated outdoor air system for office buildings in Thailand

Radiant chilled ceiling (RCC) integrated with dedicated outdoor air system (DOAS) has been considered as a system offering building occupants a good thermal comfort with energy efficiency. This paper compares three different configurations of RCC and DOAS system in terms of cooling load, room condition and energy consumption. The results from TRNSYS simulation presented that all the configurations could maintain the indoor condition with the Predictive Mean Vote (PMV) value ±0.5 over the office hours 6:00-18:00. The mean radiant temperature of the room was found below the room air temperature which resulted from the low RCC surface temperature of around 19°C. No condensation occurred on the panel during the system operation. The study showed that the RCC with DOAS comprising of cooling coil (CC), round around coil (RC) and enthalpy wheel (EW) is the most energy saving configuration.

Accidental perioperative hypothermia

The problem of perioperative hypothermia is still relevant. There are many reasons for that. One of them: a decrease in the patient’s body temperature during the operation often goes unnoticed, or is not perceived by medical staff as a serious complication. Perioperative unintentional hypothermia is a decrease in the patient’s core body temperature <36 °C in the periods: 1 h before anesthesia, during surgery and 24 h after anesthesia. Usually a decrease in body temperature activates the hypothalamic mechanisms of thermoregulation, which provide first vasoconstriction, which reduces heat loss, and then the development of cold shivering (contractile thermogenesis) – heat production. Modern anesthetics affect the regulation of central temperature and lead to its reduction in the perioperative period. Unintentional intraoperative hypothermia accompanies many surgeries performed under general and regional anesthesia. It is perhaps the most important factor in the “triad of death” (hypovolemia, acidosis, hypothermia), which significantly increases the risk of complications, including: prolongation of the duration of action of anesthetics and muscle relaxants and the recovery period; increase in the volume of intraoperative blood loss; from the cardiovascular system complications up to fatal consequences; development of wound infection, increase in wound healing time; increasing the frequency of cold shivering, nausea and vomiting in the postoperative period. Thus, perioperative hypothermia leads to an increase in hospitalization and nosocomial mortality. An important role in the prevention and relief of perioperative hypothermia is played by the competence and motivation of the nurse to timely and effective action in all areas of the perioperative process using thermometry methods available in a specific medical institution (axillary, esophageal or tympanic), prevention of heat loss through the skin under the influence of the environment (room air temperature, operating and equipment), passive and active (convection systems) heating patients with a body temperature <36 °C, rapid thawing and heating to 37 °C of allogeneic blood components. It is especially important during emergency operations, when it is necessary to start warming and temperature monitoring in the intensive care unit of the admission department.

Experimental investigation of airflow pattern and turbulence characteristics of stratum ventilation in heating mode

Stratum ventilation (SV) is feasible for heating applications. Owing to the downward supply vane angle and positive thermal buoyancy, the airflow characteristics of SV for winter heating can be distinct from those for summer cooling. This study aimed to investigate the airflow pattern and turbulence characteristics in a field environment chamber heated by SV experimentally. Twelve cases were studied with the room air temperature controlled between 19.9 and 24.3 °C. Air velocities and temperatures in the occupied zone were measured. Based on the measurements, draft risk (DR) and vertical air temperature difference between head and ankle levels (ΔT) were evaluated. The results show that the warm supply air jets were initially delivered to the zone below 1.1 m, but gradually ascended to the upper zone owing to the effect of positive thermal buoyancy. Consequently, the heights where the highest air velocity and temperature were measured varied with the distance from the supply inlets. As a result of the airflow pattern, the re-separation phenomenon of velocity spectra at different heights was observed at the far field from the inlets. These characteristics were different from those of SV for summer cooling. The airflow pattern illustrated that SV could warm the occupied zone efficiently, especially when the Archimedes number was less than 0.045. An appropriate reduction in the supply air temperature is recommended to achieve satisfactory local thermal comfort with ΔT and DR values conforming to the comfortable ranges as stipulated in ISO 7730–2005.

Evaluation of simple evaporative cooling systems in an industrial building in Poland

The use of evaporative cooling in industrial buildings is becoming increasingly popular nowadays. However, there is a lack of detailed and sufficient evaluation in the literature of simple evaporative cooling systems used in this type of buildings, particularly in the climate of Central and Eastern Europe. Therefore, this article evaluates evaporative cooling (EC) systems for an assumed industrial building located in Poland using the TRNSYS 17 software. The analysis of six systems located in four Polish cities (Koszalin, Lublin, Suwałki and Wrocław) was carried out. Simple EC systems using both direct and indirect evaporative cooling were assessed. The systems were evaluated in terms of the number of hours that each system does not reach the room air temperature setpoint (TTF), electricity and water consumption and the seasonal coefficient of performance (SCOP). The results have shown that the largest number of the TTF hours is for systems located in Lublin and the smallest in Koszalin. Depending on the analysed system, the number of the TTF hours is for Koszalin and Lublin from 178 h to 611 h and from 429 h to 1194 h, respectively. By generalizing the results, EC systems have the potential to save energy in the climate of Poland. Out of the analysed systems, the S5 system, which uses both direct and indirect evaporative cooling and only outside air for humidifying, has the greatest potential for use. It was also found that systems using outside air for humidifying instead of exhaust air reach higher energy efficiency and lower indoor air temperature more.

Narrow energy distributions of electrons emitted from clean graphene edges

This paper presents a study on electron field emission (FE) into ultrahigh vacuum (UHV) from a single, cleaned, graphene sheet where its single sheet nature has been carefully characterized and the emission zones are unambiguously the sheet edges. This definitive approach is in contrast to almost all other studies in the literature and can now guide theoretical work and applications. Our sample characterization starts with transmission electron microcopy imaging, Raman characterization, controlled mounting of individual flakes in a scanning electron microscope followed by in situ high temperature and high field treatments. Detailed FE characterization was carried out including current-voltage plots, FE microscopy, and electron energy spectroscopy during subsequent stages of sample cleaning, at room and liquid air temperatures. The full width at half maximum (FWHM) of the energy peak as well as its relative shift versus current and voltage were explored. A notable result is that the energy spectra are very narrow, ten times less than previously reported.

Dynamic performance of displacement ventilation in a lecture hall

An accurate temperature gradient calculation is essential for displacement ventilation (DV) system design since it directly relates to thecalculation of the required supply airflow rate. Inaccurate temperature prediction can cause poor thermal comfort and wrong sizing of the ventilation and cooling systems. A heat balance-based method is usually applied in displacement ventilation (DV) design when overheating is the primary indoor climate concern. The temperature gradient in DV systems is usually calculated with lumped-parameter nodal models. Several simplified nodal models were developed and implemented in the various building simulation software to estimate the temperature stratification in rooms with DV. Recent studies reveal that the multi-nodal models provide the most accurate temperature gradient prediction. However, the majority of dynamic calculation methods assumes either complete mixing of zone air or linearised temperature gradient. The present study introduces the dynamic temperature gradient model for DV and investigates the effect of thermal mass on the temperature stratification. The model was validated with the experimental results of a lecture room with displacement ventilation. The room air temperature measurements were conducted during three weeks at 20 different heights. The supply air temperature and occupancy rate were recorded during each scheduled lecture. The developed dynamic nodal model is able to calculate the air temperatures in the occupied zone accurately. The effect of the thermal mass and changing heat gains on the room air temperature stratification is analysed for the lecture room with DV.