Low Outdoor Air Research Articles

REDUCING THE INFLUENCE OF THERMAL BRIDGES IN THE BASEMENT SLAB OF CAST-IN-SITU FRAME BUILDINGS IN EXTREMELY COLD REGIONS

Introduction. Heat insulation of multi-story buildings with a reinforced concrete frame on pile foundations under climatic conditions with extremely low outdoor air temperatures is complicated by high air infiltration. When such buildings are used in winter, the most characteristic are temperature regime violations on the first floor. Purpose of the study: The study aimed to evaluate various methods to reduce the influence of thermal bridges in the basement floor of a cast-in-situ frame building with pile foundations under extreme climatic conditions. Methods: Thermal performance of 3D models of enclosing structures was determined using the certified HEAT3 program. Options of internal and external heat insulation of the basement floor with thermal breaks in the structures were considered. Results: As a result of numerical analysis of standard basement floor designs, it was established that low temperature on the inner surface and significant heat losses are associated with the presence of through thermal bridges: reinforced concrete raft — basement slab — column — concrete block masonry. The most effective solution for heat insulation of cast-in-situ frame buildings is external heat insulation of the basement floor with a thermal break in the raft. Compared to the standard solution, heat losses through the corner section of the slab with the offset column are reduced by 33.6 %, and the minimum temperature on the inner surface is higher than the dew point.

Effects on the Indoor Environment in a Stable for Horses in Winter: A Case Study

The aim of this article is to show the most significant factors influencing the indoor environment in winter considering the operating conditions of an older stable modified for housing 12 horses and an indoor riding arena for teaching and sports purposes. This research focused on assessing the influences affecting the internal environment from the point of view of the construction of the building and ventilation control in the operating conditions of working and non-working days. The analysis of the results showed that the massive masonry structure has sufficient thermal insulation and accumulation, which was manifested by good temperature stability inside the stable of 7.2 ± 1.7 °C when the outside air temperature was −4.80 ± 1.5 °C. At low outdoor air temperatures of −6.44 ± 0.4 °C, the following conditions were found: a higher relative air humidity (76.0 ± 5.3%), a high CO2 concentration 2317.1 ± 931.7 ppm, and a high airborne dust concentration PM10 = 231.94 ± 19.13 μg·m−3 and PM2.5 = 160.13 ± 6.28 μg·m−3. Therefore, it is necessary to improve the solution and function of the stable ventilation. The small size of the windows and their uneven distribution (average daylight factor ei from 0.313 ± 0.154 to 0.835 ± 0.309) caused insufficient daylight in some individual boxes.

Modelling an air handling unit, building and occupant variation regarding energy, moisture and frost protection based on measurements of an air handling unit and occupants’ moisture supply

Objectives of this paper are to propose a reasonable simulation model that can handle condensation and frost formation in heat exchangers dependent on moisture concentration and outdoor climate conditions, and to analyze risk of frost formation and discuss different frost protection strategies. Using psychometrics, American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) heat exchanger calculation, condensation and frost calculation methods, simulations models for heat recovery ventilation and energy recovery ventilation are developed. It is concluded that the risk of frost in heat exchangers is higher in northern Sweden than in southern Sweden and Denmark due to low outdoor air temperatures during the winter, however heat recovery systems in Copenhagen and Gothenburg still has a risk of frost formation even though these cities has relatively warm weather conditions. Out of several simulation models that are created during the study, the detailed model that takes condensation effect into consideration, is proven to be worthy to be used in further investigations, due to results that more accurately represent real word conditions. Risk of frost formation becomes significantly lower in every city when heat recovery ventilation is changed into energy recovery ventilation. Even though heat recovery ventilation is simulated only with the simplified model, it is safe to assume that it will still be effective in reality. Although bypass strategies were effective at eliminating the risk of frost in heat recovery units, they are not as efficient from an energy perspective. The more air is by-passed through the cross-flow plate heat exchanger, the fewer opportunities there are to recover energy from exhaust air, which leads to lower supply air temperatures and higher energy need for heating a living space.

Holistic methodology to reduce energy use and improve indoor air quality for demand-controlled ventilation

Ventilation control logics are usually based on the control indicators of occupancy. However, strategies including control of contaminants not linked to occupancy are requested and more feasible with the introduction in the market of low-cost sensors (LCS).In this work, a methodology for the improvement of demand-controlled ventilation (DCV) using measurements of IAQ parameters with LCS, correlation analysis, and co-simulation EnergyPlus/CONTAM is presented. Its goal was reduced annual energy use and the fraction of time with room air concentration of IAQ parameters outside thresholds.The ventilation control sequences of supply airflow rates and recirculation of return air focused on the significant parameters chosen by cross-correlation functions in the de-trended measurements.The results revealed that the methodology successfully developed control sequences that simultaneously reduced annual energy use and the number of hours outside the recommended IAQ guidelines compared to the baselines. In cold cities with excellent outdoor air quality, recirculation could reduce energy use and increase the RH in winter. Further simulations demonstrated that the use of recirculation had a protective effect on the indoor concentrations of PM2.5, assuming low outdoor air quality. However, when using recirculation, it is essential to control the IAQ to avoid excessive pollutants, RH, and temperatures.

The effect of internal leakage of air streams on effectiveness of the fixed-bed regenerator for fast switching cycle of its operation: experimental and numerical results

The paper presents the course of heat and mass transfer in the fixed-bed heat exchanger. For this purpose, a previously developed original mathematical model of a fixed bed regenerator was used. On the basis of the developed model, a computer program was written and verified using experimental data. The validation results confirmed that the developed model can predict the performance of the heat exchanger. The effect of the presence of internal air leaks was analyzed for conditions of sub-zero outdoor air temperatures. Multi-variant numerical simulations carried out under low outdoor air temperature operating conditions made it possible to demonstrate many irregularities. Effectiveness variation was carried out for different thermodynamic air parameters. A maximum increase in device effectiveness (up to 0.92) was demonstrated, confirmed by the additional condensation of water vapor effect and the dominant effect of “wet” area accumulation. In the analyzed cases, a decrease in “frost” area accumulation was observed (by 10%) as the relative humidity of the return air increased. Moreover, the presence of a limiting return air relative humidity (for which the dew point temperature is equal to 0°C) was demonstrated, beyond which the non-accumulated “frost” area was partially transformed to a non-accumulated “wet” zone. A significant change in the effectiveness of the device was noticeable when the relative humidity of the return exceeds 30%, which was also confirmed by the maximum size of the “frost” area for this value (about 49%).

A Low Cost Outdoor Air Pollution Monitoring Device With Power Controlled Built-In PM Sensor

Recent advances in wireless communication technology and the Internet of Things (IoT) have provided an opportunity for mass deployment of low cost sensor nodes to measure air pollution in real-time over a large geographical area. This article presents the design of a low cost, innovative Air Pollution Monitoring Device (APMD) along with the evaluation of its advanced features. An on-board Particulate Matter (PM) sensor is designed to measure PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.5</sub> and PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> . APMD additionally has electrochemical sensors to measure carbon monoxide, sulphur dioxide, nitrogen dioxide, ozone, besides temperature and humidity sensors. The node is equipped with a solar energy harvesting unit and a rechargeable battery as a backup to power up the module. By utilizing an on-board GPS subsystem, APMD packs all these gathered air quality data in a frame with physical location, time, and date, and sends them to a cloud server. The node can communicate through WiFi and NB-IoT connectivity. For validating the quality of sensing, the developed APMD was co-located with an accurate reference sensor node and a series of field data were collected over seven days. In a fully ON state, the on-board PM sensor saves up to 94% energy while maintaining root mean square error (RMSE) of 0.58 for PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.5</sub> and 2.5 for PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> . A power control mechanism is also applied on the PM sensor to control the speed of the fan by applying a pulse width modulated (PWM) signal at the switch connected to the power supply of fan. At 100 ms switching period with 30% duty cycle, the on-board PM sensor is 97% energy efficient compared to the commercial sensor, while maintaining sensing error (RMSE) as low as 0.7 for PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.5</sub> and 2.7 for PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> . Our outdoor deployment studies demonstrate that the designed APMD is 90.8% more power efficient than the reference setup with significantly higher coverage range, while maintaining an acceptable range of sensing error.

ОЦЕНКА ВОЗМОЖНОСТИ СОЛНЕЧНОГО ТЕПЛОСНАБЖЕНИЯ С ИСПОЛЬЗОВАНИЕМ ВОЗДУШНОГО ТЕПЛОВОГО НАСОСА

Solar energy is one of the sources of renewable energy. However, during the cold season in Russia, the use of solar energy is difficult due to low outdoor air temperatures. The purpose of this article is to analyze the possibility of energy saving when using solar energy for the heating system of an individual residential building in Vladivostok. The latitude of the city is 43 °, but the estimated temperature for the design of heating is -22 ° C. This greatly complicates the use of solar heat. The possibility of accumulation of low-potential heat in a specially equipped outhouse (greenhouse) for conversion by a thermal air-water pump is analyzed in order to use it for heating needs in the future. Two constructions are considered as the finishing material of the extension: a two-layer polycarbonate with an air layer and an energy-saving double-glazed window. The calculation shows that in the coldest month is January, the potential of solar thermal energy is 14 %–37 % of the required heat demand, depending on the material used in the construction of the extension. In March and April, excess heat is generated. It can be used for hot water supply needs. Thus, for an individual residential building, the use of solar heat accumulated in a greenhouse extension is relevant as an additional source of heat for the heating system.

The effect of internal leakage of air streams on effectiveness of the fixed-bed regenerator for fast switching cycle of its operation: mathematical model and numerical simulations

The paper describes an original mathematical model of heat and mass transfer for a fixed bed regenerator used to determine the effect of internal airflow leakage on heat exchanger efficiency. First, the build and operating principles of a fixed-bed heat exchanger were discussed. The presence of internal leakage was shown along with a proposed solution for its elimination. Then, a mathematical model based on a modified ε-NTU method for numerical simulation and analysis of coupled heat and mass transfer in a fixed-bed heat exchanger was presented. The model was supplemented with an additional detailed submodel designed to determine frost surface temperature and frost growth analysis. Initial numerical simulations of the operation of the model were performed for low outdoor air temperature conditions. Different zones of heat and mass transfer within the regenerator matrix were distinguished. The presence of accumulated frost area and its influence on the course of heat and mass transfer processes was revealed. In addition, the presence of a relative humidity limit curve associated with a mass balance deficiency conditioning the occurrence of frost accumulation was established.

Investigation of the Operation of Inverter Units for the Possibility of Working in the Cooling Mode at Low Outdoor Temperatures

The possibility of avoiding problems associated with low outdoor air temperatures at the design stage of the air conditioning system of a responsible object is considered. A study was conducted in laboratory conditions to determine the operability of inverter split systems at an ambient (outdoor) air temperature of “minus” 30°C. As a result of field tests in laboratory conditions, the possibility of operating inverter split systems in cooling mode at an ambient temperature of “minus” 30°C is presented.

Piston-wind ventilation strategy for thermal environment improvement of heat-supply compartment in utility tunnels

The thermal environment of the heat-supply compartment in utility tunnels is essential for the safe operation and easy maintenance of the pipeline system. Mechanical ventilation is usually employed to improve the thermal environment. However, the inevitable low outdoor air temperature in winter brings great difficulty to the mechanical ventilation effectiveness. This paper firstly performs a detailed simulation on the thermal environment in the heat-supply compartment under mechanical ventilation using the Fluent software. The results indicate that the air temperature in the first 50 m of a ventilation interval even falls below 0 °C under extreme conditions, hindering the pipeline operation and maintenance work. Therefore, a novel piston-wind ventilation strategy, which employs the piston-wind generated in a subway tunnel as the air source of ventilation, is proposed to solve the above problem. The piston-wind's applicability and superiority are validated through numerical comparison. The results demonstrate that the piston-wind ventilation exhibits higher suitability for the heat-supply compartment, since it creates superior temperature distribution than the mechanical ventilation. Further, the effect of vent size, piston-wind temperature, and piston-wind interval are simulated and discussed in detail. The results indicate that the larger vent size and the piston-wind interval between 2 and 4 min produce better ventilation effectiveness. The research finding is anticipated to provide an encouraging pathway for effective ventilation organization for the heat-supply compartment in utility tunnels.

An experimental analysis of the fluid flow on performance and frost formation in exhaust air energy recovery heat exchanger

In the present paper, results for fluid flow, temperature and air humidity experimental measurements for innovative energy recovery counterflow air-to-air heat exchanger have been shown. For the low outdoor air temperatures case, frost formation is also observed and analysed. Base on the results of analysis the temperature, humidity and total efficiency of the exchanger are presented. The analysis showed that fluid flow rate, humidity and system efficiency significantly drop down under unfavourable conditions in the winter period when the outdoor temperature decrease below -5oC. In the present system, the heat exchanger equipped with a set of opposing air dampers can use intake air to absorb the moisture from the exhaust air. This solution has the advantage to prevent the exchanger frosting as well as melt ice layer if any growth on heat exchanger walls.

Investigation of superspreading COVID-19 outbreak events in meat and poultry processing plants in Germany: A cross-sectional study.

Since May 2020, several COVID-19 outbreaks have occurred in the German meat industry despite various protective measures, and temperature and ventilation conditions were considered as possible high-risk factors. This cross-sectional study examined meat and poultry plants to assess possible risk factors. Companies completed a self-administered questionnaire on the work environment and protective measures taken to prevent SARS-CoV-2 infection. Multivariable logistic regression analysis adjusted for the possibility to distance at least 1.5 meters, break rules, and employment status was performed to identify risk factors associated with COVID-19 cases. Twenty-two meat and poultry plants with 19,072 employees participated. The prevalence of COVID-19 in the seven plants with more than 10 cases was 12.1% and was highest in the deboning and meat cutting area with 16.1%. A subsample analysis where information on maximal ventilation rate per employee was available revealed an association with the ventilation rate (adjusted odds ratio (AOR) 0.996, 95% CI 0.993-0.999). When including temperature as an interaction term in the working area, the association with the ventilation rate did not change. When room temperatures increased, the chance of testing positive for COVID-19 (AOR 0.90 95% CI 0.82-0.99) decreased, and the chance for testing positive for COVID-19for the interaction term (AOR 1.001, 95% CI 1.000-1.003) increased. Employees who work where a minimum distance of less than 1.5 m between workers was the norm had a higher chance of testing positive (AOR 3.61; 95% CI 2.83-4.6). Our results further indicate that climate conditions and low outdoor air flow are factors that can promote the spread of SARS-CoV-2 aerosols. A possible requirement for pandemic mitigation strategies in industrial workplace settings is to increase the ventilation rate.

Feasibility analysis of canceling reheating after condensation dehumidification in semiconductor cleanrooms

Cold-heat offset problem occurs due to reheating after condensation dehumidification in the make-up air unit (MAU) of semiconductor cleanrooms . This study conducted on-site measurement and analyzed the indoor thermal balance in five tested factories A-E. Based on the measured results, this study focuses on the feasibility analysis of canceling reheating to avoid cold-heat offset. It is indicated indoor condensation will not be caused in the cleanrooms. Indoor subcooling is determined by air change rates of outdoor air ( A a ) and supplied indoor air ( A s ), and heat dissipation of indoor equipment ( Q in ). The larger A a , the less A s and the less Q in , the more likely indoor subcooling will be caused. When Q in is 0–100 W/m 2 , 100–200 W/m 2 and larger than 200 W/m 2 , the requirement range of A a to avoid indoor subcooling is 7–21/h, 12–26/h and 20–26/h respectively. It is concluded that canceling reheating is possible when factories A-D is within the operating parameters. In factory E, canceling reheating is impossible since indoor subcooling is unavoidable. The performance and energy saving potential of the proposed system which cancels reheating are then analyzed. Compared with the conventional system, the required cooling capacity and heating capacity are both decreased, and the energy saving ratio of the proposed system is 10.4%–38.3%. • Cold-heat offset is prominent in both make-up unit and entire system. • Canceling reheating will not cause indoor condensation, but may indoor subcooling. • Low outdoor air change rate and high sensible load do good to canceling reheating. • Energy saving ratio of the canceling reheating system is 10.4%–38.3%.

An analysis of effectiveness of air heat pump operation dependent on change of external air temperature

Currently, air-to-water heat pumps are more widely used, which due to the high coefficient of performance reduce energy consumption and negative impact on the environment. They decrease the dependency on costs of energy resources. The work is devoted to solving the urgent problem of improving the efficiency of air heat pumps at low temperature of outdoor air in winter. One of the main problems of an air heat pump is the reduction of productivity when the outdoor air temperature decreases in winter. In this paper, the effectiveness of LG Therma V air-to-water heat pump to provide apartments with heating and hot water supply was analyzed. The heat pump is reversive, which can cool or heat a heat carrier. A four-way valve swithes the coolant flows between air exchangers. On the basis of the obtained results, plots of effectivness of the heat pump dependent on outdoor air temperature are built. It is shown that the effectiveness of the heat pump significantly depends not only on the outside temperature but also on the water temperature at the outlet of the heat pump. The use of heat pumps with a high coefficient of performance can significantly reduce energy costs. The most effective are low-temperature heating systems, in which the water temperature does not exceed 45 °C. The example is floor heating, which requires very low temperature of the floor surface – up to 30 °C. At outdoor air temperature not less than milnus 7 °C the heat pump is effective at higher temperature off heat carrier at output – up to 55 °C. To provide the uninterrupted heat supply, an additional air heater is included. It covers heat load during defrosting and very low outdoor air temperature. On the basis of the conducted researches, the directions of the further experimental and field researches are planned.

Air-Cooled Condensing Units in Thermal Engineering (Review)

Data testifying growth in the number and capacity of power plants that use atmospheric air for heat-removal purposes are presented. The basic schemes for removing heat from turbines involving air-cooled units are considered, and the ratios of their technical indicators, such as heat-transfer surface areas and power consumption for driving the pumps and fans, are illustrated. The heat-removal scheme most rational for using it in practice is substantiated. Different kinds of finning heat-transfer tubes that allow cooling system performance features to be taken into account are presented. Their design features, characteristics, and application fields are considered. Promising lines of constructing efficient heat-transfer surfaces are shown. The basic design schemes of air-cooled condensing units (ACCs), their classification, and specific features of their layout solutions are presented. The important structural components, including a large-diameter steam line, fans, and heat-exchanging modules, are described. The basic requirements for the ACC’s fan units are formulated. Their design versions, main components, and layout solutions are described. It is shown why the fan test results differ from the actual operation conditions. The basic kinds of heat-exchanging modules and their assemblies, which depend on the technological capabilities of the manufacturers and thermal-hydraulic parameters, are presented. The specific features relating to startup, shutdown, and operation of ACCs at low outdoor air temperatures are considered along with the design and technological measures taken to secure their trouble-free operation. The importance of cleaning the ACC’s finned surface is noted, and methods for cleaning it in the course of operation are pointed out. Specific features relating to the occurrence of corrosion and erosion of the ACC’s heat-transfer surface are described. The influence of wind and air recirculation on the ACC’s operation is shown, and the designs of devices for usefully utilizing the wind energy aimed at achieving more efficient operation of ACCs are suggested.

Outdoor Air-Cooling System for a Computer Room and Its Corresponding Energy-Saving Effect

The recent expansion of the internet network and rapid advancements in information and communication technology are expected to lead to a significant increase in power consumption and the number of data centers. However, these data centers consume a considerable amount of electric power all year round, regardless of working days or holidays; thus, energy saving at these facilities has become essential. A disproportionate level of power consumption is concentrated in computer rooms because air conditioners in these rooms are required to operate throughout the year to maintain a constant indoor environment for stable operation of computer equipment with high-heat release densities. Considerable energy-saving potential is expected in such computer rooms, which consume high levels of energy, if an outdoor air-cooling system and air conditioners are installed. These systems can reduce the indoor space temperature by introducing a relatively low outdoor air temperature. Therefore, we studied the energy-saving effect of introducing an outdoor air-cooling system in a computer room with a disorganized arrangement of servers and an inadequate air conditioning system in a research complex in Korea. The findings of this study confirmed that annual energy savings of up to approximately 40% can be achieved.

Development of cooling systems on the basis of absorption water-ammonia refrigerating machines of low refrigeration capacity

An analysis of the cycles of an absorption water-ammonia refrigerating machine (AWARM) is carried out in a wide range of operating parameters (temperature of the heating medium: 45...145 °C, outdoor temperature: 10...43 °C, temperature of the cooling object: minus 25...5 °C). It is shown that under the considered operating conditions, the AWARM positive effect on the energy efficiency of the AWARM is low outdoor air temperatures and high temperatures of the heating heat source. A promising cooling system based on low refrigerating capacity AWARM is developed using solar thermal energy and the technology of using natural seasonal and daily temperature potential of atmospheric air, including using night radiation cooling (NRC). The key elements of the cooling system are: storage tank; cooling system based on AWARM with combined sources of heat load; heat removal system in the mode of convection and radiation at night. It is shown that AWARM in combination with a cold storage tank allows to provide a wide range of refrigeration processing by selecting a working substance with a phase transition (melting-solidification). Working substances with a temperature level are recommended: minus 25 °C (for products of animal origin); 0 °С (primary refrigerated processing of milk); 5 °С (for fruits and vegetables). It is advisable to ensure the guaranteed heat removal from the cold storage tank of the cooling system in the passive «thermal diode» mode with the help of two-phase thermosyphons. When working with solar collectors with water, as a coolant for the AWARM generator, the AWARM scheme with a booster compressor in front of the condenser is proposed. It is shown that the greatest effect of the NRC technology in heat removal systems can be achieved in the high-mountainous regions of the planet with minimal atmospheric humidity, for example, in Kazakhstan

Features of assessment of bioclimatic comfort for modern residential buildings in hot-dry climates

The summer period is decisive for the comfort of residential construction in a hot dry climate. Modern development of residential areas in the countries of West Asian and Central Asian cities has medium and multi-storey buildings, which do not always take into account regional features and climate. Modern development of residential areas in the countries of West Asian and Central Asian cities has medium and multi-storey buildings, which do not always take into account regional features and climate. Typical climatic factors are: intensive solar radiation throughout the year; high summer temperature and low outdoor air humidity; without precipitation for five months; winds conducive to air exchange, and adverse winds from deserts, significant seasonal and diurnal temperature changes. The study of the experience of the formation of traditional folk architecture in the countries of Western and Central Asia made it possible to establish methods for design solutions that meet the requirements of an architectural and planning organization, taking into account the physical and technical factors of the urban environment. Traditional houses did not have window openings along two or three facades, as the windows faced the yard. The houses were blocked into groups, of which the residential block was formed in accordance with the type of minimal-, medium storey buildings and one or two level of roof construction. Residential groups were separated by narrow dead-end streets, which were constantly in shadow due to the overhang of the upper floors of the houses. Modern residential buildings significantly differ from the buildings of traditional quarters, used construction equipment and engineering infrastructure, which are elements of the "Smart City" concept. In this regard, it is necessary to assess the bioclimatic comfort of modern housing construction for the formation of a new quality of the urban environment and the combination of open and closed spaces.

Experimental study on cascade heat pump dryer with a solar collector under low temperature outdoor air environment

A heat pump dryer can save more energy than other dryers since its drying efficiency is 2-3 times higher than that of other types of dryers. However, the lower bound of evaporating temperature for an R134a heat pump cycle ranges from 5 to 10?C, when the outdoor air temperature closely approaches the evaporating temperature, it experiences reduced efficiency and ultimately becomes inoperable. To address this issue, a cascade heat pump dryer equipped with a solar collector was considered in order to examine the operability and efficiency of the heat pump cycle, depending on changes in the outdoor air temperature in wintertime. The changes in cascade cycles, depending on the temperature in a drying chamber, were also observed. The results showed that the average coefficient of performance (COP) of the cascade heat pump dryer was approximately 2.6 under the temperature range of ?10 to 20 ?C. An electrical heater whose COP is less than one should be used in that temperature range. It was also found that COP of the dryer increased by approximately 35% when using a solar collector under a low outdoor air temperature environment.

Experimental analysis of indoor air quality improvement achieved by using a Clean-Air Heat Pump (CAHP) air-cleaner in a ventilation system

This study investigated the air purification effect of a Clean-Air Heat Pump (CAHP) air-cleaner which combined a silica gel rotor with a heat pump to achieve air cleaning, heating and ventilation in buildings. The experiments were conducted in a field laboratory and compared a low outdoor air supply rate with CAHP air purification of recirculated air with three different outdoor air supply rates without recirculation or air cleaning. Sensory assessments of perceived air quality and chemical measurements of TVOC concentration were used to evaluate the air-cleaning performance of the CAHP. The results of the experiment showed that the operation of the CAHP significantly improved the perceived air quality in a room polluted by both human bio-effluents and building materials. At the outdoor airflow rate of 2 L/s per person, the indoor air quality with CAHP was equivalent to what was achieved in the same room with 10 L/s per person of outdoor air ventilation without air cleaning. The percentage dissatisfied was as low as 5.2% with the CAHP in operation, based on adapted perception assessment. The outdoor air supply rate can be reduced by 76% by using CAHP, as the Clean Air Delivery Rate (CADR) was over three times the outdoor air supply rate when the CAHP was in operation. The chemical measurements indicated a single-pass efficiency of over 92% for the removal of indoor air pollutants when the regeneration temperature was 60 °C. No VOC accumulation on the desiccant wheel was observed.