Actual Air Temperature Research Articles

Methodology to measure the energy flux captured by a submerged U-OWC by using temperature sensors

The estimation of the power captured by a wave energy converters (WEC) device, needs to calculate the plant efficiency. In general, it is necessary to measure both the pressure and the discharge fluctuations of the fluid motion inside the plant. Unfortunately, gauges for the direct measurement of the velocity are bulky and provide punctual measures and, especially on converters having a U-duct, the presence of the velocity sensor produces a relevant disturbance on the motion field. To overcome this issue, an alternative method to evaluate the captured energy flux, using the pressure fluctuation and the air temperature inside the plenum, was proposed by [1] and [2]. However, no information about the accuracy of the temperature sensors and consequently about the errors in estimation of the energy flux were provided.
 In this work, following the procedure described by [1] and [2], we have analysed the influence of the time response of the temperature sensor in evaluating the variation of the air volume inside the chamber and, consequently the energy captured by the plant. To this aim, the submerged U-OWC, tested directly at sea in [1], has been simulated numerically. The aim of the numerical experiment is having the actual estimation of the air temperature inside the plenum and trough it, the captured energy flux. The computational domain is constituted by a wave-flume, with a piston-type wavemaker, placed at the left extremity and a submerged breakwater embedded a U-OWC plant, in the middle. The numerical 2D unsteady simulation is based on the Eulerian approach, using the commercial code Ansys Fluent v17.0, Academic Version.
 Starting from the knowledge of the pressure fluctuation at the upper opening of the vertical duct and, of both pressure and temperature variations of the air in the plenum, we have evaluated the energy flux absorbed by the plant and we have calibrated the mathematical model used in [1] and [2], using as input the time series of the pressure fluctuations at the upper opening of the vertical duct, and the variation of both temperature and pressure of the air inside the chamber. Then, using the time series of the actual air temperature, we have simulated the input of several first order temperature sensors characterized by different time constant t, and we have analysed the percentage differences in term of energy flux as a function of t.
 We have observed that the measurements of the temperature inside the plenum are strongly affected by time constant of the sensor, which produce large errors in the evaluation of the captured energy flux.
 Finally, we have proposed a method for conditioning the measure of the air temperature, obtaining an excellent estimation of the energy flux.
 
 Boccotti, P. (2003) "On a new wave energy absorber"Ocean Engineering 30(9), pp. 1191-1200.
 Arena, F., Filianoti, P. (2007),"Small-scale field experiment on a submerged breakwater for absorbing wave energy", Journal of Waterway, Port, Coastal and Ocean Engineering, 2007, 133(2), pp. 161–167.

Performance-Based Navigation Approach Procedures with Barometric Vertical Guidance: How to Select the Air Temperature for Approach Procedure Design

In performance-based navigation (PBN) procedures with barometric vertical guidance, the effective vertical path angle (VPA) depends on the actual air temperature at the time of approach execution. A very low design temperature could result in an obstacle clearance height (OCH) higher than needed; hence, the airport throughput could be reduced when the cloud ceiling is below the OCH. Conversely, the design of a low temperature higher than is practical could lead to long periods in which the procedure cannot be used. The results of this research show that there is not much difference between the effective VPA for the different low temperatures studied. However, this slight difference, when obstacles penetrating the final approach surface (FAS) exist, usually leads to the approach minima being significantly different from each other. The objective of this study was to analyse the impact of the selected designed low temperatures in PBN procedures with barometric vertical guidance on the OCH/runway throughput and approach periods of use balance. Finally, guidelines on the selection of the minimum designed low temperature are proposed.

ANALYSIS OF ACTUAL, TYPICAL AND NORMATIVE CLIMATE DATA IN THE CONTEXT OF BUILDINGS ENERGY MODELING

This article analyses the actual, normative monthly and typical detailed climatic data for the city of Kyiv. Data on actual outdoor air temperatures during 2014-2021 were compared with indicators in accordance with Ukrainian regulations and the most common typical hourly climate files used for building energy modeling: International Weather for Energy Calculations (IWEC), Meteonorm, Typical Meteorological Year (TMY) from PVGIS tool and Onebuilding web-site. The values for outside air temperatures were compared on an average monthly basis and using the number of hours of outside air temperature duration. The latter approach allows to more accurately assess the energy efficiency indicators and energy consumption of heat supply systems with heat pumps. As the buildings energy need and energy consumption for heating values are significantly affected by heat gains due to solar radiation, a comparison of the normative value of global radiation on the horizontal surface with the values from the most common typical climatic data was also performed based on an average monthly basis. Taking into account the set of analysed climatic factors using monthly indicators for outside air temperatures and number of hours of outside air temperature duration, it is decided to use Meteonorm hourly data for Kyiv for further dynamic energy modeling of building with heat supply system based on different types of heat pumps, including the air-to-water and water(brine)-to-water ones. Also, climatic data used in RETScreen program show similar figures as normative values and therefore this program will be used for further technical and economic analysis as well and the results will be compared to the specialised program for heat pumps calculations GeoT*SOL, which also provides the detailed calculation of heat pumps system technical performance and economic calculations. In addition, possible deviations in the values of energy need for heating of the building when using different climatic data were estimated using the DesignBuilder / EnergyPlus software product. The potential deviation of energy need for heating results can be around -10…+6.5%.

Research and application of thermal insulation effect of natural gas hydrate freezing corer based on the wireline-coring principle

Natural gas hydrate (NGH) holds great promise as a source of clean energy. It is critical for acquiring the largest possible in situ NGH core for NGH eigen features and resource assessment. However, the existing NGH coring technology has limitations, such as temperature increments, limited coring diameters, low coring rates, and complex coring structures. Therefore, this study designs and proposes an NGH freezing coring (NGHFC) method and verifies the freezing and coring capacities of the NGHFC method in laboratories and experimental wells. Results suggest that NGHFC shows good freezing and heat-retention properties. A freezing core heat transfer model is developed. According to the actual air temperature and operating time, the optimum initial temperature of the cold source can be determined using this model. The average coring rate of NGHFC can reach 77.86%. The research results will provide a new idea of coring gas hydrates.

Hybrid model-based online estimation of air temperature in mobile small-scale cooling chambers

Mobile, small-scale refrigeration applications for last-mile deliveries have gained increased importance in recent years. As they face disturbances and frequent door openings more extensively than long-distance transport, reliable temperature information is crucial for control concepts to comply with temperature regulations and increase efficiency. For desired ruggedness, sensors are typically integrated within the cooling unit, yielding substantial deviations between actual air temperature in the cooling chamber and measured one — particularly in periods of altered airflow conditions resulting from fan switching and the actual door opening status. This article introduces and compares two hybrid, online estimation procedures to overcome this issue: firstly, a Kalman-filter approach based on a simple lumped physical heat transfer model, and secondly, a gray-box-model approach resulting from a realizable inversion of the physical model. Experimental investigations of typical operating profiles provide 14 h of real-world data to parameterize (11.75 h data length), validate (2.25 h data length), and compare both estimators. The proposed concepts are based on a sensor setup available in state-of-the-art system architectures and provide satisfactory temperature estimates with more than 83 % overall fit. As the algorithms provide comprehensive process insight independent of the actual operating condition, sophisticated control schemes can be built upon the concept. • Hybrid, model-based estimation approaches for air temperature in refrigerated trucks. • Kalman-filter approach based on physically motivated heat transfer model. • Gray-box-model approach resulting from realizable inversion of the physical model. • Experimental data drive parametrization, validation, and performance comparison. • Easy-to-implement algorithms offer reliable process insight for control concepts.

The impact of environmental barriers on attendance of outdoor and indoor professional sports: the case of the South Korean soccer, baseball and basketball leagues

PurposeThis study sought to determine if environmental barriers (i.e. air pollution, temperature and precipitation) affect outdoor (i.e. soccer and baseball) and indoor (i.e. basketball) professional sport attendance in South Korea.Design/methodology/approachBy including actual air quality, temperature and precipitation data collected from each place where the sporting events take place, this study conducted a regression analysis to examine factors that influenced outdoor and indoor sport attendance.FindingsIn outdoor sports, the estimated results suggested that soccer and baseball attendance were not affected by air pollution. Indoor sport consumers did not change their consumption behaviors in attending sports despite the presence of air pollution. In addition, there was mixed evidence on the effect of weather-related variables on attendance. Average temperature had a positive effect on baseball (outdoor) and basketball (indoor) sport attendance, indicating that the warmer the temperature, the more likely those fans were to attend the games. Average precipitation was negatively associated with outdoor (soccer) sport spectators.Originality/valueThe present study contributes to the sport environment literature by examining the impact of environmental barriers on spectators' behaviors in the context of outdoor and indoor professional sports.

MATHEMATICAL MODELING OF THERMAL EFFICIENCY OF BUILDING EN-VELOPE OF MULTI-STOREY BUILDINGS WITH ACCOUNT OF INDIVIDUAL INSULATION

At present, the problem of general thermal modernization of building envelopes is given much attention both at the level of scientists and consumers. This is one of the effective ways to reduce natural gas consumption, reduce the negative impact on the environment, maintain and improve comfortable indoor conditions. Over the last decade, the population has rapidly begun to insulate their homes in order to raise the indoor air temperature to a comfortable level in the multi-storey residential sector. Due to insufficient attention of the authorities in the housing and communal sector, the lack of scientific research and widespread public awareness, there is a massive thermal insulation of building by residents of multi-store buildings within their own apartments. But the study of thermal processes that occur in individual thermal insulation of enclosing structures is currently not fully completed. Therefore, in the context of significant increases in gas and electricity prices, this problem is relevant.
 In the study was carried out mathematical modeling of a fragment of a partially insulated wall of an enclosing structure with determination of heat flux by solving a three-dimensional differential equation of thermal conductivity with boundary conditions of II, III and IV kind and distribution of characteristics of building structures and insulation. These results can be used in the analysis of the efficiency of insulation of the building taking into account the fragmentary insulation and of comparison with systemic thermal modernization.
 As a result of modeling, the three-dimensional temperature fields of wall surfaces, are determined, there are additional heat fluxes (thermal bridges), which are not considered in the simplified one-dimensional calculation. In one-dimensional calculation, the heat flux from the wall is reduced by 2.43 times during insulation. Taking into account the total heat flow from the side surfaces near the window (thermal bridges) and system insulation - by 1.75 times. With fragmentary insulation and considering the total heat flux from the side surfaces near the window - by 1.6 times.
 The next stage of calculations is the determination of the actual air temperatures in the premises of a multi-storey building considering the actual condition of enclosing structures and heating systems, heaters, mode parameters of the coolant and outdoor air parameters. The methods and means of this analysis can take into account the final data of heat loss adjustment after the mathematical modeling presented in this paper. In consequence, the results will be taken into account in the projects of thermal modernization of buildings, reconstruction of heating systems, rational placement of sources, selection of equipment and regulation of devices.

Comprehensive investigations on Life Cycle Climate Performance of unitary air-conditioners

Life Cycle Climate Performance (LCCP) evaluation of air conditioning systems helps to mitigate the carbon emissions from the rapidly expanding air conditioning systems. Nevertheless, different counties have different system evaluation standards, weather conditions, grid emission factors, and material carbon emission coefficients. Furthermore, new R-410A alternatives like R-466A were rarely discussed. Besides, some researchers used the weather station data instead of onsite weather data. However, the weather data collected from the UMDCP campus and the College Park airport in the USA were different up to 5 °C due to the heat island effect. This paper used a unitary air conditioner as a case study and compared the LCCP calculation results for 11 cities worldwide for five different refrigerants. As excellent candidates for replacing R-410A from the LCCP perspective, R-32, R-290, R-452B, and R-466A are considered in this study. Then, the results using field test data and weather station data were compared. In conclusion, annual energy consumption is a significant factor in high-emission-factor countries. In some low-emission-factor countries, the LCCP can be decreased by up to 60% by using R-290. The differences between the actual inlet air temperature to the outdoor unit and local weather station measured temperature can result in up to an 8% difference in LCCP. For future work, more works on futuristic assumptions for grid emission factors and variable speed systems are needed while considering the expansion of renewable energies and energy efficient variable speed systems.

Proposals for standardization the heat transfer resistance of insulated walls of residential buildings in the Republic of Belarus

Introduction. Resistance to heat transfer is considered the main criterion of energy operational efficiency in the design of enclosing structures of buildings and structures. Therefore, the calculation of the values of the normalized resistance to heat transfer, for each locality of the Republic of Belarus, taking into account the actual outdoor temperatures and the duration of the heating season is an urgent task.
 Materials and methods. To assess the energy efficiency of enclosing structures, the value of annual heat losses Q, kWh/m2, through 1 m2 of the structure was adopted. The calculation of the values of the normalized heat transfer resistance for each locality of the Republic of Belarus, taking into account the actual outdoor air temperatures and the duration of the heating season, was carried out according to the method recommended by V.G. Gagarin. A comparative analysis of the results obtained according to the methods recommended by TCP 45-2.04-196-2010* and SP 50.13330.2012 is carried out.
 Results. The calculations determine the values of the normalized heat transfer resistance for each locality of the Republic of Belarus, taking into account the actual outdoor air temperatures during the heating period and the duration of the heating season. To facilitate the design of insulated walls, a map of the recommended (calculated) values of the heat transfer resistance of the external walls of residential buildings for the territory of the Republic of Belarus is constructed.
 Conclusions. According to the results of the performed studies, it was found that the economic efficiency in the design of insulated walls according to the method recommended by TCP 45-2.04-196-2010*, depending on the region of the Republic of Belarus for which the design is being carried out, is on average from 6 to 8 BYN per 1 m2 of insulated wall.

Urbanization contribution to human perceived temperature changes in major urban agglomerations of China

People in urban agglomerations (UAs) are increasingly exposed to elevated extreme temperature events under global warming and local human activities such as urbanization. While the urbanization effects on local temperature changes have been well studied, possibly different effects on human perceived temperature (HPT), which measures the compound influences of multiple indicators (e.g., temperature, humidity, and wind), remain much less understood. Here, we examine the long-term changes in mean and extreme HPT in 20 major UAs across the mainland of China since the 1970s, and evaluate the effect of urbanization based on a dynamic classification of urban and rural stations using time-varying land use/land cover maps. The results show that mean HPT and actual near-surface air temperature (T) in both summer and winter seasons display significant trends in most portions of China, while the frequency of extreme HPT and T events in summer (winter) exhibits increasing (decreasing) tendency. These trends are particularly stronger in more populated and urbanized UAs. It is estimated that urbanization averagely accounts for around 1/6 of the total increasing trend in mean HPT and T in the urban core areas of 20 UAs. In both seasons, the effects of urbanization on mean HPT are more profound than T. Moreover, urbanization significantly increases the occurrence frequency of summertime hot extremes and decreases the occurrence of wintertime cold events. Regionally, northern UAs in general exhibit more remarkable trends than the south. The urbanization process exerts more prominent effects in HPT than T in nearly three-quarters of all UAs, except several regions with a complex topography and lower urbanization level. These findings reported here can provide suggestions and support for urban planning of decision-maker and human perceived thermal comfort choices of humans living in UAs.

Vertical microclimate heterogeneity and dew formation in semi-closed and naturally ventilated tomato greenhouses

The extent of the vertical microclimate heterogeneity inside a greenhouse is mostly unknown, and it can strongly affect plant production and yield quality. Tomato crop was grown in a semi-closed greenhouse equipped with horizontal ventilation and sidewall curtains, which were only opened depending on microclimate conditions; and a naturally ventilated greenhouse equipped with sidewalls curtains that were kept open. Both greenhouses had a 1,000-m2 area and a net size of 50-mesh, and were located in an arid climate zone in Israel. Vertical profiles of CO2 concentration, actual vapor pressure, air, leaf and soil temperature, net CO2 assimilation rates, stomatal conductance, and total fruit yield, fresh mass, and quality were monitored in both greenhouses for 13 days, in January 2018; CO2 concentration, actual vapor pressure, and air and soil temperature were additionally monitored in the semi-closed greenhouse for seven days in December 2016, when the ventilation was inoperative, and in December 2017, with ventilation. The vertical air temperature gradient, along with the colder microclimate inside the naturally ventilated greenhouse, led to a lack of plant uniformity and yield loss. Closing the side curtains in the fanned semi-closed greenhouse had a beneficial effect on yield, however, with mixed results for quality, due to the higher air temperature and lower carbon dioxide levels at the upper canopy. Horizontal air circulation in the semi-closed greenhouse increased transpiration and assimilation, and increased dew occurrence at night, but did not reduce the vertical heterogeneity. Significant vertical gradients affect plant physiology, and closing the curtains in winter cultivation in semi-arid/arid climates has the potential to improve fruit yield and quality. However, it must be coupled with proper air circulation and, preferably, with CO2 enrichment, or careful management of natural ventilation through side curtains, in order to maximize CO2 replenishment while minimizing heat losses.

Computational fluid dynamics simulation wall model predicting air temperature of the nasal passage for nonhuman primates.

Nasal passages adjust the temperature of inhaled air to reach the required body temperature for the lungs. The nasal regions of primates including humans are believed to have experienced anatomical modifications that are adaptive to effective conditioning of the atmospheric air in the habitat for a given species. Measurements of the nasal temperature are required to understand the air-conditioning performance for a given species. Unfortunately, repeated direct measurements within the nasal passage have been technically precluded in most nonhuman primates. Computational fluid dynamics (CFD) simulation is a potential approach for examining the temperature profile in the nasal passage without any direct measurements. The CFD simulation model mainly comprises a computational model to simulate physiological mechanisms and a wall model to simulate the nasal passage's anatomical and physical properties. We used a computational model developed for humans and examined corrections for the developed wall model based on human properties for predicting its performance in Japanese macaques. This study confirmed that the epithelium layer thickness of the wall model affects the accuracy of the predictions for macaques. A convenient correction of the thickness based on body mass allows us to simulate the actual air temperature profile in macaques' nasal passage. The CFD simulations of the wall model corrected with body mass can be applied to other nonhuman primates and mammals. This convenient corrective approach allows us to examine the functional contributions of a specific morphology to the air-conditioning performance without any direct measurements to improve our understanding of primates' functional morphology and physical adaptations to the temperature environment in their habitat.

Transient sensor errors and their impact on fixed-bed regenerator (FBR) testing standards

Fixed-bed regenerators (FBRs) are a favorable option for energy recovery in building HVAC systems due to their high sensible effectiveness. Unlike other types of energy recovery exchangers, the air temperature at the outlet of FBRs varies with time, which creates challenges when measuring the outlet temperature and effectiveness of FBRs since the actual outlet air temperature will include the transient response of the FBR and the temperature sensor. In this article, a validated numerical model of FBRs that takes into account the sensor response is used to quantify the temperature and effectiveness errors that result due to sensors’ response characteristics over a wide range of design parameters. The main contributions of this article are the practical recommendations for the temperature measurement for different types of FBRs developed for HVAC applications. The recommendations presented in this article could be implemented in future versions of the current standards (ASHRAE 84 and CSA C439-18 standards) for performance testing of air-to-air energy exchangers.

Thermal performance of a lightweight building with phase change material under a humid subtropical climate

Ø The effect of PCMs under various climate conditions was investigated. Ø A simulated model was developed and verified against experimental data. Ø Energy use intensity (EUI) was used as the index to evaluate PCM performance. Ø An economic analysis was conducted using static investment payback period. The use of phase change materials (PCMs) in building enclosures is an efficient way to reduce the heat gain and/or loss in summer and winter. It was evident that the thermal performance of buildings with PCMs was affected by the outdoor air temperature significantly. However, the influence of humidity, which was serious in the humid subtropical climate was unclear. To explore the effect of PCMs under a humid subtropical climate, the thermal performance of a lightweight building outfitted with PCMs with a melting temperature of 25 °C was investigated. The actual outdoor air temperature with a humidity of 40–90 RH% and wind velocity of 2–6 m/s blowing from the east, west, south, and north was assumed for the performance assessment. A simulated model was developed using EnergyPlus and verified against experimental data. The energy savings by using PCMs was reduced from 3.9% to 2.6% when the outdoor humidity increased from 40 to 90 RH% in summer. However, the savings was not obvious in winter. Annual energy savings decreased from 1.64% to 1.32% with humidity increasing from 40 to 90 RH%. For annual condition, the average energy savings was reduced from 1.43% to 0.92% when the wind speed increased from 2 m/s to 6 m/s. From an economic point of view, the investment payback period was less than 10 years when the PCM price was lower than 18.0 Yuan/kg.

The impact of accurately modelling corridor thermodynamics in the overheating risk assessment of multi-residential dwellings

Prolonged overheating can have serious cumulative effects on human health, resulting in heat exhaustion, heatstroke and even death. The frequency and severity of heatwaves will increase considerably in the future as a result of accelerating climatic changes compounded by increasing urbanisation.A recent overheating risk-assessment methodology, Technical Memorandum (TM)59: 2017 was developed by the Chartered Institution of Building Services Engineers (CIBSE) to address this problem, by providing a consistent framework for the evaluation of overheating risks in new homes. TM59 has for the first time highlighted the importance of including corridor heat transfer effects in the dynamic modelling of multi-residential dwellings. This paper investigates the strengths and limitations of current approaches to the modelling of corridors, based on a case study of three energy-efficient flats located in London. The results of modelling in accordance with TM59 guidance are compared with alternative approaches, using more realistic occupancy and weather information, and compared to empirically measured data. The findings of this study indicate that current practices in Building Performance Simulation (BPS) are likely to under-estimate the actual air temperatures in corridors. This study highlights the need for further research into the way in which corridors, flats and their interconnecting ventilation and heat transfer networks are commonly discretised in BPS models.

Evaluation of natural gas saving measures in public educational institutions

The article analyzes the data of gas consumption for the heating periods and confirms that for the actual outdoor air temperatures there is a decrease in gas consumption. Necessary heat loads and gas consumption were determined to ensure the required indoor air temperature in the premises of the educational buildings with the proposed mode of gas savings by lowering the indoor air temperature, the so-called economical mode of operation of the boiler room. The theoretical economy of gas from lowering the temperature regime is determined. To increase the accuracy of the experiment, the comparison of the amount of gas consumed was performed in terms of working and non-working periods of the day. Based on these studies, it should be noted that the actual plot can be used to determine the actual gas savings in real conditions.

УДОСКОНАЛЕННЯ МЕТОДУ НОРМУВАННЯ ВИТРАТ ПАЛЬНОГО АВТОБРОНЕТАНКОВОЇ ТЕХНІКИ НАЦІОНАЛЬНОЇ ГВАРДІЇ УКРАЇНИ

In the development of fuel consumption rates, various methods are applied: analytical (calculated), calculated-statistical and experimental. The fuel and lubricant consumption rates for military units of the National Guard of Ukraine are designed to plan and control their consumption, maintain records, introduce a saving mode and rational use of specific fuel consumption rates. An analytical method for fuel consumption rationing based on an improved fuel consumption model is proposed. The method involves the use of a new classification of operating conditions of armored vehicles National Guard of Ukraine, in which the road and transport conditions are quantitatively estimated by the average technical speed, and the atmospheric and climatic conditions by air temperature and height above sea level. An important advantage of the method is the possibility of individual rationing of fuel consumption by military units of the National Guard of Ukraine with the help of computer technology for actual average daily speeds, air temperature and height above sea level. Based on the obtained scientific results, which constitute a single complex of research (assumptions, mathematical models, dependencies), a comprehensive classification of operating conditions of the armored vehicles is proposed. A unified classification should be widely used in the development of various norms and standards, solving transport problems, planning and managing transport processes. The development of an improved system for taking into account operating conditions is possible provided that the optimal number of parameters characterizing the operating conditions of armored vehicles National Guard of Ukraine is taken into account.

A method for determining vegetation growth process using remote sensing data: A case study in the Three-River Headwaters Region, China

Accurate measurements of the associated vegetation phenological dynamics are crucial for understanding the relationship between climate change and terrestrial ecosystems. However, at present, most vegetation phenological calculations are based on a single algorithm or method. Because of the spatial, temporal, and ecological complexity of the vegetation growth processes, a single algorithm or method for monitoring all these processes has been indicated to be elusive. Therefore, in this study, from the perspective of plant growth characteristics, we established a method to remotely determine the start of the growth season (SOG) and the end of the growth season (EOG), in which the maximum relative change rate of the normalized difference vegetation index (NDVI) corresponds to the SOG, and the next minimum absolute change rate of the NDVI corresponds to the EOG. Taking the Three-River Headwaters Region in 2000–2013 as an example, we ascertained the spatiotemporal and vertical characteristics of its vegetation phenological changes. Then, in contrast to the actual air temperature data, observed data and other related studies, we found that the SOG and EOG calculated by the proposed method is closer to the time corresponding to the air temperature, and the trends of the SOG and EOG calculated by the proposed method are in good agreement with other relevant studies. Meantime, the error of the SOG between the calculated and observed in this study is smaller than that in other studies.

Templates for Modeling Temperature Response of Passive Greenhouses

A previous publication [1] Stiles, M. 2018. “A Simple Model for Temperature Response of Single Zone Passive Buildings,” Journal of Building Physics, April 2018. Available at http://journals.sagepub.com/doi/full/10.1177/1744259118763843 (last accessed November 27, 2018). [Google Scholar] introduced a model of interior air temperature response to exterior temperature for a single-zone structure with no active heating, ventilation, or cooling. The model was based on a simple exponential step response function relating the two temperatures. Results were sufficiently encouraging to apply the model to other simple passive structures. This article applies the model to two cases of passive greenhouses. One of the greenhouses is a rudimentary plastic-covered hoop house. The other is a super-insulated net-zero structure that grows summer crops in cold climates using sunlight as the source of heating. A model for the interior air temperature of both of these structures was developed using two time-series templates. The first template is an exponential step response function of outdoor air temperature. This template synchronizes the model to the actual interior temperature but does not match its amplitude. A second template was developed by subtracting the model using the first template from the actual interior air temperature data. The second template scaled according to available sunlight as measured by an inexpensive photometric sensor. The superposition of the two templates tracks the actual interior temperature reasonably well given the limitations described in this article. Average difference between actual and modeled data for both structures was within 2°F, although maximum deviations ranged up to 30°F. This article concludes with a discussion of refinements to the model and of its commercial deployment should it prove generally applicable to passive greenhouses.

A method to obtain precise determinations of relative humidity using thin film capacitive sensors under normal or extreme humidity conditions

Abstract Dampness is one of the worst, and most common problems found in heritage buildings and sites. However, despite its relevance, sensors do not operate satisfactorily in extremely humid environments. The paper analyses the performance of heated capacitive sensors conceived to operate at ambient temperature (T) and very high relative humidity (RH) after having been demisted with short heating. Even if they show better performances than traditional, unheated sensors, they operate at the limit of their range, with severe limitations affecting their time response and accuracy, reducing but not excluding false readings. A method is proposed to combine temperature and relative humidity sensors, and warm-up them in order to reach the best performance interval of the RH sensor, and take measurements in such conditions, i.e. at higher temperature and lower relative humidity. From the combined temperature and relative humidity readings it is possible to calculate the dew point that is invariant to temperature changes. Combining the dew point with an additional measurement of the actual air temperature, it is possible to calculate the actual relative humidity. The use of this method is not necessarily limited to taking more accurate relative humidity readings under extreme dampness, but it may be also applied to improve the quality of readings with sensors that operate in their best performance interval. The same strategy can be used in too dry environments with cooling to raise relative humidity and bring the sensor into the best performance interval.