Relative Humidity Control Research Articles

Effects of heat and different humidity levels on aerobic and anaerobic exercise performance in athletes

Previous studies suggest that the maximum oxygen uptake (VO2max) and the Wingate anaerobic test performances are decreased in hot environments, but it is unknown whether humidity changes in a hot environment further affect the results of the VO2max and Wingate anaerobic test. Nine male athletes performed VO2max and Wingate anaerobic tests under three environmental conditions: (1) 21 °C/20% relative humidity (R.H.) (control); (2) 33 °C/20% R.H. (hot–dry); and (3) 33 °C/80% R.H. (hot–wet). The participants' weight, oral temperature, and skin temperature were recorded pre-exercise and postexercise. The heart rate was monitored continuously throughout the exercise. Compared to the control condition, the hot–dry and the hot–wet conditions had lower VO2max values (control at 3779.0 ± 234.3 mL/min vs. hot–dry at 3528.2 ± 467.4 mL/min and hot–wet at 3595.9 ± 274.6 mL/min; p < 0.05). However, there was no difference in the VO2max between the hot–dry and the hot–wet conditions. A decrease in the postexercise oral-to-skin temperature gradient was strongly correlated with decreased VO2max (mL kg−1 min−1) in all conditions (r = 0.835, p < 0.001). There was no significant difference between the conditions in the peak power and anaerobic capacity during the Wingate anaerobic test. The VO2max was impaired in the hot–dry and in the hot–wet conditions, compared to the control condition; however, the different humidity levels (i.e. hot–dry vs. hot–wet) had no effect on the VO2max. The postexercise oral-to-skin temperature gradient was in line with the variance in VO2max in all three different environmental conditions. The Wingate anaerobic test performance was not affected by the hot–dry or the hot–wet conditions, compared to the control environment. These results suggest that different relative humidity conditions do not affect the VO2max or the Wingate anaerobic test performance in hot environments.

Technical Note: New methodology for measuring viscosities in small volumes characteristic of environmental chamber particle samples

Abstract. Herein, a method for the determination of viscosities of small sample volumes is introduced, with important implications for the viscosity determination of particle samples from environmental chambers (used to simulate atmospheric conditions). The amount of sample needed is &lt; 1 μl, and the technique is capable of determining viscosities (η) ranging between 10−3 and 103 Pascal seconds (Pa s) in samples that cover a range of chemical properties and with real-time relative humidity and temperature control; hence, the technique should be well-suited for determining the viscosities, under atmospherically relevant conditions, of particles collected from environmental chambers. In this technique, supermicron particles are first deposited on an inert hydrophobic substrate. Then, insoluble beads (~1 μm in diameter) are embedded in the particles. Next, a flow of gas is introduced over the particles, which generates a shear stress on the particle surfaces. The sample responds to this shear stress by generating internal circulations, which are quantified with an optical microscope by monitoring the movement of the beads. The rate of internal circulation is shown to be a function of particle viscosity but independent of the particle material for a wide range of organic and organic-water samples. A calibration curve is constructed from the experimental data that relates the rate of internal circulation to particle viscosity, and this calibration curve is successfully used to predict viscosities in multicomponent organic mixtures.

Identifying causes of mechanical defects and critical control points in fruit supply chains: an overview of a banana supply chain

The issue of food losses is of high importance in the efforts to combat hunger, raise income and improve food security in many developing countries. Therefore, there is need to minimise food losses in agri-food supply chains. This study was conducted with the aim to identify causes of mechanical defects in banana fruit supply chain in Zimbabwe and to also establish critical control points at which incidence of the mechanical fruit defects can be minimised in the chain. Data was gathered through interviews and participatory observation. Most of the causes of mechanical defects were found to be due to poor handling at the different stages in the chain. Propping, maturity at harvest, handling during harvesting and packing, and control of temperature and relative humidity during fruit ripening were established as critical control points at which incidence of mechanical damage can be minimised.

A coupled numerical approach on museum air conditioning: Energy and fluid-dynamic analysis

In the museum environment, the temporal stability and the spatial uniformity of the indoor microclimatic parameters are necessary primarily for the correct artwork conservation and then for the occupant thermal comfort. Therefore, a HVAC system is usually necessary.This paper above all emphasizes the integration of Building Energy Performance Simulation (BEPS) and Computational Fluid Dynamics (CFD) codes. This coupled numerical approach can provide accurate information about both the HVAC system energy request and the indoor microclimatic control (temporal and spatial distribution of the parameters).Then, a case study concerning a typical museum exhibition room is examined.The annual energy request for three types of all-air system, as well as the temporal variation of indoor temperature and relative humidity, is evaluated by means of a BEPS code. Energy savings can be obtained using a system with desiccant wheel (11%) or enthalpy wheel (9%), compared to the base system. As regards indoor relative humidity control, this is more critical for summer conditions, and the best performance is obtained by the system with desiccant wheel.Then, the spatial microclimatic control is analyzed by means of a CFD analysis, for various thermal load conditions and different air diffusion xequipments. The best performances are obtained by using the swirling (vortex) diffusers; also the perimetrical stripes of slot diffusers show satisfactory performances. Finally, in order to evaluate the ability of air diffusion equipments to assure good ventilation effectiveness, an analysis of the mean age of air is carried out too.

Tratamento de sementes de trigo com zinco: armazenabilidade, componentes do rendimento e teor do elemento nas sementes

O objetivo do presente estudo foi avaliar os efeitos do tratamento de sementes de trigo com zinco na armazenabilidade, teor de zinco nas sementes e nos componentes de rendimento da cultura. As sementes foram recobertas com as doses 0, 1, 2, 3 e 4mL de sulfato de zinco (ZnSO4 kg-1) mais fungicida, polímero e água e, em seguida, foram armazenadas por seis meses, em ambiente sem controle de temperatura e umidade relativa do ar. Antes da semeadura, as sementes foram avaliadas pelo teste de germinação e, após a colheita pelos componentes do rendimento: número de espiguetas por planta, número de grãos por espigueta e peso de grãos por planta, sendo que, após o armazenamento de seis meses, avaliou-se o teor de zinco nas sementes. O recobrimento com zinco não prejudica a viabilidade das sementes de trigo armazenadas por seis meses, além de promover aumento no número de grãos por espigueta e no peso de grãos por planta. O teor de zinco nas sementes aumenta linearmente com o incremento das doses de ZnSO4 via recobrimento.

NEW PHYTOTRON FOR STUDYING THE EFFECT OF CLIMATE CHANGE ON PLANT PATHOGENS

The Intergovernmental Panel on Climate Change in its recent fourth assessment report predicts that, because of higher concentrations of greenhouse gases in the atmosphere, until 2100 the global mean temperature would rise between 0.6 and 4°C, in combination with changes in precipitation and an increased frequency of extreme weather events. Despite this trend, the extent and mechanisms through which elevated CO&lt;sub&gt;2&lt;/sub&gt; affects plant diseases remain uncertain. Increases in CO&lt;sub&gt;2&lt;/sub&gt; and temperatures are also expected to induce complex effects on plant pathogens. Although re- 10 search on the effects of climate change continues to be limited, new tools are permitting to study the effects of climate variables on infection rates in the case of some pathosystems. The shortage of critical epidemiological data on individual plant diseases needs to be addressed using experimental approaches. A useful tool for such types of studies is represented by phytotrons. Hereby, a new phytotron typology, built with the specific aim of studying the effect of climate change on plant disease, is described. Beginning from a general plant overview, key mechanical and electrical systems are described (i.e. air temperature and relative humidity control, lighting and CO&lt;sub&gt;2&lt;/sub&gt; control system etc.) as environmental parameters and operation cycle are summarized. In particular both parameters which could be set and monitored and those measured and stored are reported. After a suitable testing period, several operation cycles were performed in order to assess the control system’s stability and to optimize the management of all systems involved and the first experimental trials were carried out. The effect of three different simulated climatic conditions: 450 ppm of CO&lt;sub&gt;2&lt;/sub&gt; with standard temperature (ranging from 18 to 24°C or 18 to 26°C), elevated CO&lt;sub&gt;2&lt;/sub&gt; (800 ppm) with standard temperature and elevated CO&lt;sub&gt;2&lt;/sub&gt; (800 ppm) with elevated temperature (4°C higher than standard) on the development of grape powdery and downy mildew were tested.

Ion-induced nucleation rate measurement in SO2/H2O/N2 gas mixture by soft X-ray ionization at various pressures and temperatures

This paper reports the systematic investigation of ion-induced nucleation rate measurement in a SO2/H2O/N2 gas mixture, employing soft X-ray at different pressure and temperature levels. Experiments were conducted using a modified continuous flow gas-generation system employing a soft X-ray ionizer and a particle counter, with an improved integrated online temperature, pressure and a relative humidity (RH) control system. Nucleation rates were measured as a function of SO2 concentration at different levels of RH, pressure (600–970hPa) and temperature (5–25°C). The results show that the nucleation rate dependence on SO2 concentration followed a power law, and the slope varied slightly in a range from 1 to 1.26 at different RH levels (15–60%). A positive pressure effect was generally found and a power law was followed with varied scaling for different SO2 concentrations. The trend of an increase in nucleation rate with temperature was consistent with observations in homogenous nucleation experiments, and with the behavior predicted by classical binary nucleation theory. These experimental results will be useful to explain the contribution of ion-induced nucleation in different locations and atmospheric conditions.

Environmental chamber for in situ dynamic control of temperature and relative humidity during x-ray scattering

We have designed, constructed, and evaluated an environmental chamber that has in situ dynamic control of temperature (25 to 90 °C) and relative humidity (0% to 95%). The compact specimen chamber is designed for x-ray scattering in transmission with an escape angle of 2θ = ±30°. The specimen chamber is compatible with a completely evacuated system such as the Rigaku PSAXS system, in which the specimen chamber is placed inside a larger evacuated chamber (flight path). It is also compatible with x-ray systems consisting of evacuated flight tubes separated by small air gaps for sample placement. When attached to a linear motor (vertical displacement), the environmental chamber can access multiple sample positions. The temperature and relative humidity inside the specimen chamber are controlled by passing a mixture of dry and saturated gas through the chamber and by heating the chamber walls. Alternatively, the chamber can be used to control the gaseous environment without humidity. To illustrate the value of this apparatus, we have probed morphology transformations in Nafion(®) membranes and a polymerized ionic liquid as a function of relative humidity in nitrogen.

Impact of precipitation dynamics on net ecosystem productivity

AbstractNet ecosystem productivity (NEP) was measured on shortgrass steppe (SGS) vegetation at the USDA Central Plains Experimental Range in northeastern Colorado from 2001 to 2003. Large year‐to‐year differences were observed in annual NEP, with &gt;95% of the net carbon uptake occurring during May and June. Low precipitation during the 2002 April to June time period greatly reduced annual net carbon uptake. Large precipitation events (&gt;10 mm day−1) promoted carbon uptake, while small precipitation events (&lt;10 mm day−1) enhanced heterotrophic respiration and resulted in a net loss of carbon from the system. Large precipitation event enhanced carbon uptake was attributed to increased soil water content (SWC), which promotes plant photosynthesis. The large precipitation events which occurred from July to October have lower increases in daytime net CO2 uptake (NEPd) due to the presence of low live plant biomass compared to earlier in the growing season. Live aboveground plant biomass (AGB), solar radiation, and SWC were the major variables that controlled NEPd, while AGB, SWC, and relative humidity control nighttime respiration losses (NEPn). Aboveground plant biomass is the most important variable for controlling both NEPd and NEPn dynamics. These results suggest that the major factor controlling growing season NEPn is the amount of carbon fixed via photosynthesis during the day. Heterotrophic soil respiration is greatly enhanced for one to 2 days following rainfall events with daily rainfall events &gt;5 mm having a similar increase in respiration (&gt;3.00 g m Cm−2 day−1). In addition, the size of the heterotrophic respiration pulse is independent of both the amount of time since the last rainfall event and the time of occurrence during the growing season.

Changes in the effects of weathering and mechanical damage on soybean seed during storage

Summary The physiological quality of seeds of early and semi-early soybean cultivars may be lower than desired as a consequence of unfavorable climatic conditions occurring during the harvest period. The objective of this research work was to evaluate the effects of field weathering as well as the levels of mechanical damage at harvest on soybean seeds during storage, as determined by the tetrazolium (TZ) test. Seeds from two lots of each of three semi-early soybean cultivars (CD 214 RR, BRS 184, and Embrapa 48) with two different levels of initial vigour (high and medium) on the basis of the germination and accelerated ageing tests were stored in Mandaguari County, in the State of Parana, in storage facilities without environmental (temperature and relative humidity) control. Seed evaluations were performed using the tetrazolium test at 45 d intervals for a total of 225 d of storage. The parameters determined by the tetrazolium test were weathering (TZ class 3), and mechanical damage (TZ classes 6 to 8). It was concluded that weathering and mechanical damage injury increased substantially during storage, progressing linearly for the three cultivars studied and independent of the initial level of seed lot vigour. The classification of mechanical damage was only divided into two categories (immediate and latent damage) therefore further evaluations will be needed to accurately determine actual characteristics as well as their correlation with the loss of physiological quality of soybean seeds during storage.

Humidity control can compensate for the damage induced in protein crystals by alien solutions.

The use of relative humidity control of protein crystals to overcome some of the shortcomings of soaking ligands (i.e. inhibitors, substrate analogs, weak ligands) into pre-grown apoprotein crystals has been explored. Crystals of PurE (EC 4.1.1.21), an enzyme from the purine-biosynthesis pathway of Bacillus anthracis, were used as a test case. The findings can be summarized as follows: (i) using humidity control, it is possible to improve/optimize the diffraction quality of crystals soaked in solutions of organic solvent (DMSO, ethanol) containing ligands/inhibitors; (ii) optimization of the relative humidity can compensate for the deterioration of the diffraction pattern that is observed upon desalting crystals grown in high salt; (iii) combining desalting protocols with the addition of PEG it is possible to achieve very high concentrations of weak ligands (in the 5-10 mM range) in soaking solutions and (iv) fine control of the relative humidity of crystals soaked in these solutions can compensate for the deterioration of crystal diffraction and restore `high-resolution' diffraction for structure-based and fragment-based drug design. It is suggested that these experimental protocols may be useful in other protein systems and may be applicable in academic or private research to increase the probability of obtaining structures of protein-ligand complexes at high resolution.

Development of Relative Humidity Control Cell for Infrared Absorption Spectrum Measurement and its Applications for the Study of Clay Minerals

Development of Relative Humidity Control Cell for Infrared Absorption Spectrum Measurement and its Applications for the Study of Clay Minerals

In-situ confocal Raman observation of structural changes of insulin crystals in sequential dehydration process

In-situ confocal Raman spectroscopy combined with relative humidity (RH) control technique was used to study the sequential dehydration process of insulin crystals. By gradually decreasing the ambient RH of the insulin crystal, the content of the hydration water in the crystal was quantitatively controlled. Tyrosine (Tyr) residues were very sensitive to the micro-environmental changes, and four Raman features 828cm−1, 852cm−1, 1174cm−1 and 1206cm−1 of Tyr were employed to monitor the dehydration process. Taking advantage of the ratios I852/I828 at different RH values, the mole fractions of the ‘exposed’ and ‘buried’ Tyr residues were estimated. Moreover, using the ratio I1174/I1206 as an indicator of the dehydration process, three RH regions were discriminated. This is believed to imply that different types of the hydration water were lost step by step, i.e. firstly the ‘second-layer’ and ‘first-layer’ classes, then the ‘contact’ class, and finally, the ‘inside’ class. In addition, the profile of the amide I band was observed to gradually change with RH. By band fitting of the amide I region, changes in secondary structure were quantitatively determined. And the results showed that nearly 17% of α-helix converted into β-sheet with RH decreasing from 92% to 2%.

Analysis of vehicular cabins’ thermal sensation and comfort state, under relative humidity and temperature control, using Berkeley and Fanger models

This manuscript discusses the effect of manipulating the Relative Humidity (RH) along with the Dry Bulb Temperature (DBT) on vehicular cabins’ environment in terms of the overall thermal comfort and human occupants’ thermal sensation. The study uses the Berkeley and the Fanger models to investigate the human comfort through analyzing the (RH) effect from three specific perspectives; firstly its effect on other environmental conditions such as the Dew Point Temperature (DPT), the Enthalpy (H), the vapor pressure (vp) and the humidity ratio (ω) in the cabin. This will be done during the summer and winter periods. Secondly, the cabin local sensation (LS) and comfort (LC) will be analyzed for different body segments mainly; the head, chest, back, hands and feet with the addition of the overall sensation (OS) and the overall comfort (OC). This will be done using a thermal manikin based on the Berkeley model. Thirdly, the human sensation will be measured by the Predicted Mean Value (PMV) and the Predicted Percentage Dissatisfied (PPD) indices during the summer and the winter periods using the Fanger model calculations. From this study and according to the Berkeley model; the RH value should be controlled and synced with the cooling process such that at the early stage (rapid transient) low RH value should be enforced; while a high RH value is needed in the steady state phase. During the start of the heating process (winter conditions), the RH value does not play a major role due to low temperature in the passenger compartment. However, at later periods until the end of the heating process, a low RH value is needed to achieve the needed comfort level. According to Fanger model, in the summer period as the RH value increases, the A/C can achieve the human comfort zone ( PMV = ∓0.5) in lesser time than if the RH value is not controlled. While in the winter period, as the RH value decreases, the A/C reaches the human comfort zone faster. So, this study shows that controlling the relative humidity along with (DBT) enables the cabin to reach the comfort zone faster than the sole control of the cabin (DBT), in both the cooling and the heating processes i.e. summer and winter conditions respectively.

A theoretical study of inlet relative humidity control in PEM fuel cell

In this paper, the individual roles of inlet anode and cathode humidification, and their influences on PEM fuel cell’s electrical performance are discussed systematically by using a pseudo two-dimensional, two-phase PEM fuel cell model. It follows that the maximum power density point of a PEM fuel cell is strongly dependent on the combination of the inlet anode and cathode humidification conditions. Their influences, however, are predicted to be highly asymmetrical, with the anode and cathode humidification mainly affecting ohmic and concentration overpotential, respectively. The physical explanation to this asymmetry is given with the aid of a detailed set of simulation results. Finally, the developed understanding of their influences are employed to formulate two examples on the use of inlet relative humidity control as a simple and effective method for maximizing the volumetric power density and operating range of PEM fuel cell, respectively.

Efficacy of home-style dehydrators for reducing Salmonella on whole-muscle chicken.

Home-style dehydrators commonly used by consumers have limited relative humidity (RH) and temperature control. To evaluate the effect of dehydrator load on temperature and RH and subsequent reduction of Salmonella on whole-muscle chicken, chicken breasts were rolled and cut into samples (1 to 2 mm thick, 6 by 6 cm(2)) and inoculated with a five-strain Salmonella cocktail. The samples were allowed to air dry for 15 min and then were loaded into home-style three-tray (3T) or five-tray (5T) dehydrators, with 12 chicken pieces per tray. No difference (P > 0.05) was observed in RH or temperature between the 3T and 5T dehydrators. Peak RH was 38% and gradually deceased to 8.5% after 6 h of drying. Temperatures peaked at 57 °C after 6 h of drying. Dehydrator load had no effect (P > 0.05) on lethality for Salmonella. A reduction of 3.3 ± 0.2 log CFU/cm(2) was observed after 6 h of drying. However, sample location affected Salmonella reduction (P < 0.05). Samples from the bottom tray had a 1.5-log reduction, whereas samples from the top and middle trays had 4.1- and 3.9-log reductions, respectively. The water activity of samples after 6 h of drying was 0.71 ± 0.17 regardless of tray location or dehydrator type. When chicken was dried in home-style dehydrators, increasing the dehydrator load did not increase RH or achieve greater Salmonella lethality. Tray location had a significant impact on Salmonella lethality. Adequate reduction of Salmonella on chicken was not achieved when chamber temperatures were below 57 °C with limited RH throughout drying.

Effect of relative humidity and temperature control on in-cabin thermal comfort state: Thermodynamic and psychometric analyses

Abstract This manuscript discusses the effect of manipulating the Relative Humidity RH of in-cabin environment on the thermal comfort and human occupants’ thermal sensation. The study uses thermodynamic and psychometric analyses, to incorporate the effect of changing RH along with the dry bulb temperature on human comfort. Specifically, the study computes the effect of changing the relative humidity on the amount of heat rejected from the passenger compartment and the effect of relative humidity on occupants comfort zone. A practical system implementation is also discussed in terms of an evaporative cooler design. The results show that changing the RH along with dry bulb temperature inside vehicular cabins can improve the air conditioning efficiency by reducing the heat removed while improving the Human comfort sensations as measured by the Predicted Mean Value PMV and the Predicted Percentage Dissatisfied PPD indices.

The Optimization of Temperature and Relative Humidity Control in Cushing Library

Cushing Library located on Texas A&amp;M University campus is a special building, which needs precise temperature and relative humidity control, because it stores a number of rare collections and memorial books. This paper will concentrate the unit, which serves the book stacks. This AHU is a multiple zone, constant air volume (MZCAV) system, with reheat and direct digital control (DDC). It has a standard cooling coil, glycol cooling coil, steam humidifier, and heat recovery. Because of programming problems and hardware problems, the relative humidity was not controlling properly. In this paper, the new control program for temperature and relative humidity control is implemented and the energy savings from the new control program is estimated.

Modelling the response of Lechago earth and rockfill dam

Lechago dam (Teruel, Spain) is a 40 m high zoned earth and rockfill dam sitting on soft continental deltaic deposits. A relatively narrow central clay core is stabilised by wide rockfill shoulders. The dam was well instrumented and continuous records of stress development, pore-water pressures and vertical displacements are available for the construction period. Compaction conditions were followed by means of laboratory and in situ control tests. Core clay material was investigated by means of tests performed on compacted specimens of tertiary clays. Rockfill samples were excavated in outcrops of highly fractured Cambrian quartzitic shale. A testing programme on compacted rockfill gravels was conducted under relative humidity control in a large-diameter oedometer and triaxial cells. A coupled finite-element model has been developed to analyse the tests performed and dam behaviour during construction. Model predictions, essentially based on laboratory tests, are compared with measurements during construction. The predicted response of the dam under an assumed programme of impounding is also given. In the future, once impounding occurs, it will be possible to compare these predictions with actual dam performance. The paper provides an integrated description of the dam design, construction and early behaviour. It presents a procedure to interpret available data (laboratory as well as in situ data) on compacted materials from the perspective of modern constitutive models. It also provides an evaluation of the capabilities of advanced numerical tools to reproduce the measured dam behaviour.

ADAPTACIÓN DE UN MODELO DE DETERIORO A SEMILLAS DE TOMATE DE CÁSCARA

Los factores ambientales más importantes que afectan la viabilidad de semillas almacenadas son la humedad relativa y la temperatura. En esta investigación se adaptó un modelo diseñado para tomate (Lycopersicon esculentum Mill.) para estimar la viabilidad de semillas de tomate de cáscara (Physalis ixocarpa Brot.) almacenadas sin control de temperatura ni de humedad relativa. El contenido de humedad de las semillas de tomate de cáscara se calculó usando la temperatura y la humedad relativa del almacén, y la viabilidad con la ecuación de Ellis y Roberts. Se calibró el coeficiente lambda (λ) de la ecuación que calcula el contenido de agua de la semilla, así como los parámetros CH, CW, CQ, y Ki, simultáneamente y por separado, con los métodos de optimización Marquardt y Simplex mediante mínimos cuadrados ordinarios, para minimizar la diferencia entre la viabilidad modelada y la observada. Como medidas de sesgo se calculó el error medio de la diferencia entre valores observados y modelados (MBE), el error medio en porcentaje (MPE) y la raíz cuadrada de la diferencia media (RMSD). La lambda calibrada (61.6) para tomate de cáscara, fue 62 % superior a la del tomate, pero con la calibración se obtuvo un promedio apropiado (5 %) de humedad de la semilla. La mejor calibración de la ecuación de viabilidad de Ellis y Roberts fue cuando se optimizaron simultáneamente CH, CW y Ki con el método Simplex; así los parámetros variaron en menos de 4.6 % de su valor original, el error medio de porcentaje fue 3.4 %, y el R2 fue 0.97. Según el modelo optimizado, viabilidad de la semilla fue mayor o igual a 85 % hasta 263 d de almacenamiento, y luego perdió 50 % de viabilidad en cuatro años y cinco meses.