Relative humidity, relationships temperature

Analysis of Environmental Data. Although the methodology for analyzing the data has been previously reported ( ) there are some differences that should be noted. First, a later version of the RAPS data base was used as an initial sourse. Second, time-of-wetness in this paper is defined differently, thus, a relationship to calculate relative humidity from temperature and dew point is based on data for dew points greater than 0 C. Third, deposition velocities are calculated from boundary layer theory rather than empirical relationships. 

Difference in membrane pretreatments and other experimental conditions such as cell geometry, data analysis, humidification, and temperature can cause variability in proton conductivity data. Zawodzinski et al. studied the proton conductivity of Nafion 117 membrane as functions of membrane water content. The results show the conductivity decreases roughly linearly with decreasing water content. Sone et al. reported the dependence of conductivity of Nafion 117 membrane on both relative humidity and temperature. The conductivity of Nafion 117 without heat treatment was 7.8 x 10- S/cm at ambient temperature and 100% RH (vapor). When water content (water per acid site) increased from 2 to 4, the proton conductivity increases exponentially, and above 4, this relationship is linear. The conductivity of the membrane decreases with the increase of temperature from 20°C to 45°C due to loss of water. In contrast, from 45°C to 80°C, the conductivity increases with temperature since the water content remains rather constant, and the activation energy was lower than 2 kJ/mol. Kopitzke et al. carried out a study of the temperature dependence of the ionic conductivity of Nafion 117-H+ membranes. ... 

Fig. 1. Relationship between the moisture content of wood (% of dry wood) and relative humidity at different temperatures.

Temperature Although ambient temperature would be expected to have an influence on the rate of rusting, its effect is not clearly defined despite the efforts of workers to establish a relationship . It has an effect on relative humidity and consequently an indirect effect on corrosion. However, fluctuations in temperature may be more important than average temperatures because they influence condensation and the rate of drying of moisture in contact with steel. 

Figure 2.4 shows the equilibrium relationships of biological materials between the water content and the water activity, at constant temperatures and pressures. These data were first published in 1971, but did not find much attention in the RM field until now. At equilibrium the water activity is related to the relative humidity cp of the surrounding atmosphere (Equation 2.3) where p is the equihbrium water vapor pressure exerted by the biological material and po the equilibriiun vapor pressure of pure water at the same temperature. 

While many sets of data appear to follow Eq. (VV) relatively well, with slopes of mr 1 as predicted, deviations in the values of mT and br are often observed. There are a number of reasons for such deviations (e.g., see Pankow and Bidleman, 1992). For example, changes in temperature, concentrations of SOC, and relative humidity during sampling, nonattainment of equilibrium, and sampling artifacts can all lead to deviations from the predicted, equilibrium relationship. In addition, if (A7/d AHvap) in Eq. (UU) is not constant along the series, relationship (VV) will not hold because the value of ft. is changing. 

Perhaps the most direct experimental means of examining the relationship between emissions and air quality is to simulate atmospheric conditions using large chambers. Measured concentrations of the primary pollutants are injected into these environmental (or smog) chambers, as they are called. These are then irradiated with sunlight or lamps used to mimic the sun, and the time-concentration profiles of the primary pollutants as well as the resulting secondary pollutants are measured. The primary pollutant concentrations as well as temperature, relative humidity, and so on can be systematically varied to establish the relationship between emissions and air quality, free from the complexities of continuously injected pollutant emissions and meteorology, both of which complicate the interpretation of ambient air data. 

Clearly, such experiments can be used to examine the relationship between primary emissions and the formation of a host of secondary pollutants. For example, runs can be carried out at varying initial concentrations of hydrocarbon and NO, and the effects on the formation of secondary pollutants such as 03 studied. The reactivity of various hydrocarbons can be examined by studying them singly or in combination. In addition, such parameters as temperature, relative humidity and total pressure, presence of copollutants, and spectral distribution of the light source can be systematically varied. 

The acid number determinations were made immediately after refinement of the oil and were continued at every biological test period for 325 days. The oil was applied at 100% concentration to the point of runoff on immature bean and corn plants in the greenhouse. The temperature at which the plants were grown for the duration of each test was 80 F., and the relative humidity was approximately 85%. Phytotoxicity was determined on the second, seventh, and fourteenth day after the plants were sprayed. Figure 1 demonstrates the relationship obtained in these tests between acid number and per cent of plant injury. 

To obtain water vapor concentration, output signal intensity by TDLAS is calibrated under a well-controlled environment in variation of relative humidity and surrounding temperature. Figure 10 shows a relationship between water vapor concentration and output signal intensity detected by TDLAS. It is shown that the... 

The Arrhenius relationship of the property degradation rates of uncoated silk over a range of temperatures was determined. A temperature of 150°C was found to be inappropriate for the accelerated thermal aging of silk because of the large effect on the extrapolated reaction rate at 20°C for tensile properties and also because of the amount and hue of color developed. In addition, changes in the relative humidity affected the degradation rate of tensile properties and yellowing only above a level of 50%. 

Table I shows the overall variation in the weights when the simulated-flood procedure was applied to similar pairs of identical books over an 8-mo period. The simulated flood was applied to these books as if they were loosely packed on the shelf—i.e., stored with minimum pressure applied to them. The relationship of each book s dry weight with the temperature and relative humidity of the room appears to have been comparable. The variability of the wetting action of both types of books is also similar however, the variances (the standard deviation squared) associated with the weights of the drained books are significantly different (statistical significance reported at the 95% confidence level unless otherwise noted) by use of an F-test (3). Since the handling of book pairs—i.e., one uncoated- and one coated-paper book—was the same in preparing samples for subsequent restoration studies, it might be concluded that drainage water from the books containing uncoated paper could be different from books with coated paper.

The relationship between the regain of wool and the relative humidity at three different temperatures is shown in Fig. 2.13. 

The purpose of this study was to evaluate laboratory formaldehyde release test methods for predicting real-life formaldehyde air concentrations human exposure levels, and health risk. Three test methods were investigated the European perforator test, the gas analysis method at 60 C and 3% RH, and the gas analysis method at 23 C and 55% RH. Different types of particleboard bonded with urea-formaldehyde and urea-melamine-formaldehyde resins were tested. The results were used to rank boards as a function of test method, conditioning, short-term humidity, and temperature variations during storage. Additional experiments were conducted in small experimental houses at a Dutch research institute. Our conclusions are that relative ranking of products is influenced by the test method and by change in relative humidity. The relationship between test method and release in real-life situations is not clear. In fact, it seems impossible to use laboratory measurements to predict real-life product performance of board if the board is not fully in equilibrium with the atmosphere. 

Time-of-wetness as previously defined was the time exceeding some critical relative humidity ( ), In this paper time-of-wetness is the time a critical relative humidity is exceeded and the dew point is greater than 0 C, plus any time the critical humidity is not exceeded and it is raining. For that reason a regression relating relative humidity to dew points above 0 C and temperature was used to calculate relative humidity for each hour. This relationship is ... 

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