Humidity control system

This type of sensor utilizes a drastic increase in resistance at the point of dew condensation, since water absorption swells the polymers to counteract ohmic contact between carbon particles. This type sensor is now widely applied to humidity controling systems of video tape recorders or car windows. 

Nearly all types of coating processes will benefit from a consistent process air dew point. Humidity control systems may be complex, incorporating dehumidifiers (for dew point reduction to about 5-iO C). desiccant dryers (for products requiring low product temperatures and dew points below 0 C), steam humidifiers (to increase dew point in cold, dry weather), etc. It is suggested that laboratory trials be conducted to evaluate product and process sensitivity to variations in inlet air dew point. 

ORP needs to be exposed to air, thus the heat is released to the surrounding environment throughout the whole reaction. In the case of long-time use, the accumulative effect of heat cannot be overlooked because this will necessitate a temperature and humidity control system of higher quality. 

Zagorzycki investigated the technical and economic feasibility of humidity control systems applied to conveyor dryers such as tobacco dryers [43,44]. The humidity at any point in the dryer is controlled by the adjustment of the volume of exhaust flow. In this case study, it has been shown that applying control technology to conveyor dryers offers substantial cost savings. 

Figure 3. Costs for space conditioning by various humidity controlling systems (adapted from...

Figure 11-54 is a photograph of a commercial Kathabar air-dehydration unit manufactured by the Kathabar Systems Division of Somerset Technologies, Inc. The Kathene solution used in this unit is a solution of lithium chloride with appropriate additives. Kathabar humidity control systems are offered by the Kathabar Systems Division of Somerset Technologies, Inc. 

Deodorant materials and humidity control systems these applications are obviously based on adsorption properties of MOFs. One example of removal of tetrahydrothiophene (10-15 ppm) from natural gas by using electrochemically prepared Cu-btc-EMOF is described in Ref. [41]. The materials are capable of adsorbing up to 70g of the sulfur compound per liter of MOF, which is an order of magnitude larger than the values obtained for carbon adsorbents. 

Most xenon arc testers simulate the effects of moisture through water spray and/or humidity control systems. The limitation of water spray is that when relatively cold water is sprayed onto a relatively hot test specimen, the specimen cools down. This may slow down the degradation. However water spray is very useful for simulating thermal shock and erosion. In a xenon arc, highly purified water is necessary to prevent water spotting. Because humidity can affect the degradation type and rate of certain indoor products, such as many textiles and inks, control of relative humidity is recommended in many test specifications. Modern xenon test chambers are available with relative humidity control. 

Fermentation. The term fermentation arose from the misconception that black tea production is a microbial process (73). The conversion of green leaf to black tea was recognized as an oxidative process initiated by tea—enzyme catalysis circa 1901 (74). The process, which starts at the onset of maceration, is allowed to continue under ambient conditions. Leaf temperature is maintained at less than 25—30°C as lower (15—25°C) temperatures improve flavor (75). Temperature control and air diffusion are faciUtated by distributing macerated leaf in layers 5—8 cm deep on the factory floor, but more often on racked trays in a fermentation room maintained at a high rh and at the lowest feasible temperature. Depending on the nature of the leaf, the maceration techniques, the ambient temperature, and the style of tea desired, the fermentation time can vary from 45 min to 3 h. More highly controlled systems depend on the timed conveyance of macerated leaf on mesh belts for forced-air circulation. If the system is enclosed, humidity and temperature control are improved (76). 

Engineering factors include (a) contaminant characteristics such as physical and chemical properties - concentration, particulate shape, size distribution, chemical reactivity, corrosivity, abrasiveness, and toxicity (b) gas stream characteristics such as volume flow rate, dust loading, temperature, pressure, humidity, composition, viscosity, density, reactivity, combustibility, corrosivity, and toxicity and (c) design and performance characteristics of the control system such as pressure drop, reliability, dependability, compliance with utility and maintenance requirements, and temperature limitations, as well as size, weight, and fractional efficiency curves for particulates and mass transfer or contaminant destruction capability for gases or vapors. 

In addition to the building parameters, there are often some requirements from suppliers of processes and equipment to make sure their parts function properly. This may mean that the requirements for the equipment decide the target levels (e.g., in pharmaceutical and electronics industries). In other cases there are restrictions on deviations from the target levels (e.g., on temperature for machine control system or on humidity and vibration for optical measure nient systems). ... 

Humidification can be achieved by placing separate humidifiers directly in the conditioned space. In order to maintain the design conditions, however, humidity control should be incorporated into the system. When positioning humidifiers, care has to be taken to ensure that the leaving moisture does not impinge on adjacent surfaces, forming lime or algae deposits. 

Because of these solutions, important technical data can be transferred from local instrumentation (control system) through data-based controllers to a control station with computers. The operator may use the many variations that the software data system provides. Technical data operation may be digital off/on messages such as the status of operation and the performance of alarms or analog measurements such as temperature, humidity, pressure, velocity, energy usage, etc. 

Environmental Condition for Process Measurement and Control Systems Temperature and Humidity Electrical Instruments in Hazardous Locations, Ernest C. Magison, 1978... 

An air conditioning system uses an assembly of equipment to treat air. Normally the assembly includes a heating system for modifying winter indoor temperature and humidity a refrigeration system for modifying summer temperature and humidity, a means to maintain indoor air quality (i.e., air filters and fresh air intake) a method of distribution of conditioned air and a control system, such as a thermostat, to maintain desired comfort conditions. 

Both electronic and microcomputer-based controls require information about the state of the controlled system. Sensors convert different physical variables into an electric signal that is conditioned and typically converted to a digital signal to be used in microcontrollers. The trend in the construction techniques of modern sensors is the use of silicon microstrnctures because of the good performance and the low cost of this type of device. In the energy control scope the main quantities to be measured are the temperature, pressure, flow, light intensity, humidity (RH), and the electric quantities of voltage and current. 

With such systems, it is possible to obtain individual room space heating and humidity control without the need to dispatch an engineer to check every room in the building. Manpower costs can be reduced, with the staff being required for checking and maintenance purposes only. The cost of an energy management system can be recovered in a relatively short period of time (of the order of 2-3 years). 

In building control the controlled parameters include basic functions such as discharge air temperature, space temperature, humidity and fan control. The benefits of such a control system in an intelligent, integrated heating and cooling network include repeatable and individual parameter or area (zone) control. Individual comfort control has been shown to increase employee output and provide an annual productivity gain of over 1000 per employee. 

The conditions in which the system will be used (i.e., will it be used on the interior or exterior of buildings, does it require light or humidity controls, etc.). Most card reader systems can operate under normal environmental conditions, and therefore this would be a mitigating factor only in extreme conditions. 

When it is important to control the water activity in a reactor, a water activity sensor is quite useful. The sensor should ideally measure the water activity in the liquid reaction medium. However, the sensors available are designed for gas phase measurements, and, provided there is effective enough equilibration between the liquid and gaseous phases, they can be used to control the water activity in the reactor. If the measured water activity is above the set point, drying is initiated, for example, by passing dry air through the reactor. On the other hand, if the water activity is too low, water can be added, either as liquid water or as humid air. Automatically controlled systems of this kind have been successfully used to monitor and control enzymatic reactions in organic media [13, 14]. 

The production of gas sensors. The production records of various types of gas sensors for past five years in Japan are listed in Table I except for the oxygen and humidity sensors. The sensors produced in the largest quantity are of the semiconductive type, followed by the catalytic combustion and thermistor types. These sensors have been mostly applied to domestic uses such as gas leakage alarms or gas control systems for LP gas and town gas which are extensively used for cooking and heating in Japanese houses. This is why these sensors are manufactured on a large scale. Other electrochemical sensors have been developed mainly to monitor other gases. 

Humidity sensors consist of two major types, i.e., one which measures relative humidity and the other which detects dew condensation. The sensors for relative humidity made of ceramic or organic polymers are produced in amounts exceeding one million. They are applied to controling systems in air conditioning, micro wave ovens, and so on... 

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