Temperature Humidity Control Research Articles

Research on the influence of air humidity on the annual heating or cooling energy consumption

Just taking 960 m 2 model building with improved envelope for example, this paper studies the influence of outside air humidity on the annual heating and cooling energy consumption and their relative variation rates (RVRs) and the discrepancy between temperature–humidity control (THC) and temperature control (TC) with the same increase of ventilation rates. The research shows that the discrepancy of annual heating and cooling RVRs is significant under different climatic conditions for the same building with the same increase of ventilation rates by the mode of THC. In general, the heating RVRs decline with the increase of average outside air humidity and the cooling RVRs rise with the increase of average outside air humidity. However, annual heating and cooling RVRs are both approximate in different cities under the climatic conditions of approximate annual average air humidity. The annual heating or cooling need by mode of THC is higher than or equal to the corresponding energy consumption by mode of TC and there exists a close relationship between the absolute increment of energy consumption and outside air humidity; furthermore, as the annual average air humidity increases, the absolute increment of annual cooling need increases while that of annual heating need decreases and both have good linear relation.

An Evaluation of Heating and Ventilation Control Strategies for Livestock Buildings

Thermal responses and supplemental heat consumption of a livestock building airspace were investigated using a simulation program and Typical Meterological Year weather data for a cold (-23 to -32°C) and a warm day (-4 to 7°C) in the Canadian Prairie Region. Three different control strategies using different sizes of heating/ventilating equipment and different controller time constants were evaluated. In an either-or-temperature (EOT) control, stage 1 ventilation was provided continuously by fan 1; stage 2 ventilation and the heater were controlled by the same temperature actuated switch such that either the heater was on or stage 2 ventilation fan 2 was on, but not both. In an either-or-neither temperature (EONT) control, stage 1 ventilation was provided continuously and the heater and stage 2 ventilation were controlled by separate actuated switches with a fixed interstage differential. In a temperature-humidity control (THC), all stages of ventilation were controlled thermostatically and the heater was controlled by a humidistat. THC control strategy provided the best thermal response and used the least supplemental heat. EOT control could achieve a variable ventilation rate for moisture control when fans and heater were correctly designed. EONT control provided good temperature control but failed to control humidity. Oversizing of heating/ventilating equipment resulted in poorer thermal response and higher energy consumption for EOT and EONT systems but had little effect on the THC system. Controllers with large time constants economized the use of supplemental heat but introduced poor thermal responses for all three control strategies.

Variable Ventilation Rate Control Below the Heat-deficit Temperature in Cold-climate Livestock Buildings

Steady-state and transient analysis of three control strategies, either-or temperature (EOT) control, either-or-neither temperature (EONT) control, and temperature-humidity control (THC) are reported in this article. Variable ventilation rates, temperature and relative humidity responses, and supplemental heat consumption were simulated using a dynamic thermal environment model for livestock buildings. Variable ventilation rates following the moisture balance curve can be approximated by using an EOT control strategy and properly sized fans and heaters. The first-stage fan should have a flow rate equal to that required for moisture balance control at the design outside temperature. The second-stage fan, when added to the first-stage fan, should provide a flow rate to meet the ventilation requirement at the heat-deficit temperature. The heater capacity must closely match the supplemental heat requirement at the design outside temperature. Practical difficulties in accurately sizing heaters and fans will limit the application of EOT control. The EONT control strategy does not automatically adjust the ventilation rate during the heating season but it is a better alternative than EOT control for short heating season barns. The THC involved sensing both temperature and humidity and was shown to be superior to temperature-only control strategies in terms of the ventilation rate modulation to simultaneously achieve the design indoor temperature and relative humidity.

Simultaneous control of temperature and humidity in a confined space: Part 1—methmatical modeling of the Dynamic behavior of the temperature and humidity in a confined space

A pair of nonlinear differential equations which describe the transient behavior of temperature and humidity in a confined space have been derived from simultaneous material balances of dry air and water along with the enthalpy balance of moist air. The equations are sufficiently general to take into account external heat loads, and internal heat and moisture loads within the confined space. Since temperature-humidity control systems allow usually only small deviations of temperature and humidity from a desired operating point, a linearization of the above equations within the bounds of small deviations is justified. Hence the nonlinear equations are linearized around a desired steady state operating point. On using available relations for the specific volume and enthalpy of moist air, the linearized equations further result in a pair of linear uncoupled differential equations. The response from the linear equations is found to compare very favorably with that from the original nonlinear equations.

Simultaneous control of temperature and humidity in a confined space: Part 2 — feedback control synthesis via classical control theory

Classical control theory is used to synthesize feedback controllers for the simultaneous control of temperature and humidity in a confined space. The decoupling or diagonalization approach is employed to reduce the multivariable control system to a pair of noninteracting control loops and the Ziegler-Nichols settings are then determined for each loop. The temperature-humidity control system is then compared with conventional temperature-only control systems.

On the Analog Simulation of Control System of Phytotron. (III)

Dynamic-characteristic of temperature-humidity control system in Phytotron is obtained by analogsimulation.Temperature and humidity are not separative in this control system. So, interference of these variables causes complex phenomena. Characteristic of this two variable control system is made clear by examination of analog-simulation.

The importance of airborne contamination as a factor in postoperative wound infection.

Among the factors involved in postoperative wound infection, the effect of airborne contamination in the operating room has been considered of major importance, and substantial efforts have been directed toward minimizing its influence.^1-10A unique situation created by an affiliation between two hospitals with identical surgical staff but with markedly different operating room designs provided an opportunity to assess this influence. Figure 1 shows the floor plan of the self-contained isolated operating room (OR) suite of Misericordia Hospital, a recently built 340-bed voluntary institution. The suite has an independent temperature-humidity control unit. Extraneous traffic is not admitted, and each operating room has an adjacent scrub area. Figure 2 shows the operating suite at Fordham Hospital, a 420-bed municipal institution built in 1907. The shaded area indicates public corridors. The elevators and staircases shown open directly on the OR corridor and are the only such facilities for general use. All