Space Heating Processes Research Articles

Studies on alternative hybrid materials for replacement of R134a in space heating process

Abstract This paper exhibits the performance analysis of a heat pump framework utilizing pure refrigerants and zeotropic refrigerant mixtures. In the current work R407c has been blended with R134a and the performance and energy consumption patterns are studied. The work is carried out without doing any modifications to the compressor. The main idea behind the work is to replace the R134a with R407c to some extent in the existing systems without doing any modifications. It can be concluded that refrigerant mixtures have the potential of competing with pure R134a. In case of mixture the COP is less due to the lesser critical temperature of the mixture which reduces the heat absorbing capacity and hence COP. Thinking about the ongoing patterns of substitution of R134a, in the present examination, RR407c can be a potential HFC refrigerant trade for new and existing frameworks by and by utilizing R134a with least investment and efforts.

Field measurement and estimate of gaseous and particle pollutant emissions from cooking and space heating processes in rural households, northern China

Abstract Pollutant emissions into outdoor air from cooking and space heating processes with various solid fuels were measured, and daily household emissions were estimated from the kitchen performance tests. The burning of honeycomb briquette had the lowest emission factors, while the use of wood produced the highest pollutants. Daily emissions from space heating were significantly higher than those from cooking, and the use of honeycomb briquette for cooking and raw coal chunk for space heating reduces 28%, 24% and 25% for CO, PM10 and PM2.5, compared to wood for cooking and peat for space heating. Much higher emissions were observed during the initial phase than the stable phase due to insufficient air supply and lower combustion temperature at the beginning of burning processes. However, more mass percent of fine particles formed in the later high temperature stable burning phase may increase potential inhalation exposure risks.

Sustainable Energy in Building Systems

Sustainable energy in buildings refers to efforts to reduce or eliminate the need to burn fossil fuels for space heating and cooling. In the USA buildings use one-third of our total energy, two thirds of electrical energy and one eighth of water. U. S. Green Building Council (USGBC), that promotes sustainability in how buildings are designed, built, and operated has designed or introduced a Leadership in Energy and Environmental Design (LEED) green building rating system.*(1) It has been helping professionals across the country to improve the quality of buildings and their impact on the environment. More and more building professionals, owners and operators are seeing the benefit of green buildings and LEED certification. Green design reduces the operating costs, enhances building and organizational marketability, and increases occupant productivity.In existing buildings, energy sustainability can be accomplished through increased efficient energy use, in conjunction with decreased energy consumption and/or reduced consumption of conventional energy sources. In these buildings, fossil fuels are burned on-site as primary energy and off-site to generate electricity for secondary energy.Heating is most often needed in an occupied space in the seasonal cold climate regions of the world. Higher energy consumption and costs involved with meeting this need motivates us to find ways to improve the efficiency of the existing processes. Convective heating is the most popular type of heating which heats the space by blowing air to transfer heat across the heating coil. As most of the manufacturing facilities are built to have higher ceilings to accommodate all the equipment, the convective space heating process is energy inefficient for the needed ambient temperature. Also, as it is air that is heated up during the convective heating process and it tends to leak across the shell of the building losing the energy, especially in the manufacturing plants, most of which are housed in very old buildings. In addition, using the convective heating tends to heat up whole air to maintain the given spaceat certain needed temperatures. Also most of the convective heaters are capable of achieving a maximum of 85% efficiency. The actual efficiencies might be a bit lower than that.The students and the staff of the Bradley University Industrial Assessment Center (BU IAC) have assessed about 425 manufacturing plants in the states of Illinois, Indiana, and Missouri since 1993. A majority of these plants were housed in very old buildings with envelopes in very poor repair. Many buildings were found to have no insulation and with several openings. This was resulting in high space heating costs and thermal discomfort for the occupants.The purpose of the work reported in this paper was to explore the feasibility of radiant space heating as a sustainable energy for space heating in manufacturing plants. Several case studies based upon the work done by the staff and students of the BU IAC are presented in this paper. BU IAC is a U. S. Department of Energy (DOE) sponsored program with the objective of implementing energy efficiency and cost savings for small and medium sized manufacturing plants while educating tomorrow's energy engineers. Currently there are 24 such centers in the country and Bradley University has one of them since 1993. Success stories of the DOE's IAC program are discussed in the paper.

Research of the Grid-Tied Power System Consisting of Wind Turbine and Boiler GALAN

Space heating system consisting of small-scale wind turbine and boiler GALAN is proposed and researched in this paper. Usually boiler GALAN is fed from the electric grid. The proposed system has the small wind turbine with permanent magnet synchronous generator, which feeds the boiler when the wind is blowing. In case when wind speed is too low, the boiler is fed from electric grid. In cases when the boiler does not consume all power of wind turbine or in summer, feeding of the boiler can be disconnected and the surplus power of wind turbine is supplied into electric grid. The two-step controller is used for the control of the space heating process. The power of wind turbine is also supplied into the electric grid during the pauses of power supply to the electrode boiler. The boiler can be additionally fed from the electric grid when power of the wind turbine is insufficient. Mathematic description and model for the proposed space heating system was worked out and researched. Research of the mathematical model disclosed that the system based on small-scale wind turbine and boiler GALAN is viable. The proposed system allows diminishing of the bills for electricity consumed for the space heating in a desirable amount.

Improved Control Strategies for Electric Space Heating Processes

This paper describes three new control strategies for the discontinuous control of electric space heating processes. Discontinuous controllers are invariably used for such processes in order to reduce the cost of control. The disadvantages of such systems are the large overshoots and undershoots, large periods of oscillation, and offset errors. The first strategy utilizing an ON-OFF controller with derivative feedback is shown to minimize the magnitude of oscillations, the period of oscillation, and offset errors. The second strategy utilizes a three-position controller with derivative feedback. Besides eliminating oscillations and offset errors, the controller enables a time optimal start-up of the process. By minimizing the deadzone in the controller, sensitivity to disturbances is increased. A simple method of designing such a controller is also indicated. The third strategy utilizes a pulsewidth modulated (PWM) controller for processes where power is available either at its maximum rating or no power at all. By a proper choice of the parameters, it is shown that the magnitude of oscillations and the period of oscillation can be controlled by the designer. Offset error is completely eliminated, indicating a more effective utilization of power. All the three strategies described require only a minor modification of the existing controllers; the resulting improvement in performance is expected to compensate the slight increase in cost of control. The mathematical derivations involved in the design and analysis of such controllers have deliberately avoided, since the presentation is specifically intended for practicing engineers.

Mode-Dependent Time Constants in Electric Heating Processes

Adequate comfort conditions in any space heating process can be assured only if a good understanding of the dynamic temperature variations is possessed. The vast majority of published literature considering the system dynamics assumes that the temperature variations have an exponential increase or decrease with time, and hence, that the thermal system can be modeled by linear RC equivalent circuits. These linear models have a severe restriction in that the time constant of the exponential variations remain constant under all conditions. A few published articles giving experimental data have indicated that in discontinuously controlled electric heating processes the system time constant during heating (active time constant) is not necessarily the same as the system time constant during the interval in which no heat is supplied (passive time constant).

Discontinuous temperature control

1.6 million homes were solely electrically heated in the United States in 1963; by 1980, the predicted number is 19 million. In most of these residences temperature is controlled by a 2-position line-voltage thermostat in each room. Suitable continuous and quasicontinuous temperature-control systems have been developed, but the price trend of the semiconductor devices they employ indicates that they will not successfully compete with line-voltage thermostats in the next decade. The 2-position line-voltage methods currently available in the United States have economic and discomfort disadvantages. Facile graphical displays of the extra heating costs caused by cycle time and droop have been derived from a basic electrical-network analogue for the electric space-heating process. Test results illustrate the cold-air currents caused by long cycle times. 2-position controlled skirting-board heaters are prone to deposit dirt on walls; this tendency increases with cycle time. The performance of a discontinuously controlled electric space-heating process is conveniently characterised by portraying the cycle time, manipulated variable and droop in a cycling-characteristic display. The current problems of 2-position line-voltage-controlled electric space heating could be remedied if two performance requirements were set. Recommended values for these are suggested; these can be met if simple design criteria are observed, as is shown using a sample thermostat constructed from standard components.

Quasi-Continuous Temperature Control in the Electric Space Heating Process

Quasi-continuous temperature control is needed when electric space heating is applied to temperature-dependent processes. In such applications, multiposition systems cannot supply the accurate control often required, and quasi-continuous systems have economic and operating advantages over many continuous systems. The reference input of a quasi-continuous system can be a trimmed, optimized, open-loop command derived from the incoming and outgoing quality levels of the process. Feedforward correction for process lag, and overriding commands, can easily be incorporated into such systems. Quasi-continuous characteristics contain a number of discontinuities. Time can be saved by representing these characteristics by a continuous profile. A multitude of intermediate values of manipulated variable can be obtained by new and inexpensive methods. When the heating load must remain intact, phase-discontinuity methods can be used which approximate level-discontinuity control. For fast response processes, phase-controlled SCR's (silicon-controlled rectifiers) can be used. The T-T (temperature-time) diagrams have limitations as representations of quasi-continuously controlled processes. Time domain information can be obtained from the phase plane where quasi-continuous performance resembles a spiral. Nonlinearities can be advantageously introduced into quasi-continuous profiles. Performance is improved by derivative feedback. It is possible to predict quasi-continuous system behavior by means of a 3-dimensional actuating-signal display.

Multiposition Discontinuous Temperature Control in the Electric Space Heating Process

Three new schemes for 3-position temperature control are described. A new method is introduced for analyzing and predicting the behavior of a multiposition temperature control system by displaying its actuating signal equation in three dimensions. Two new methods of predicting or analyzing the behavior, in the phase plane and time domain, of the multiposition temperature-controlled electric space heating process are described. Expressions are derived for the evaluation of the important performances indexes and figures of merit of such multiposition controlled processes. A new display method is outlined for simultaneously portraying the phase-plane and time-domain performance of such processes. Cycling characteristic diagrams are shown for 3-position controlled electric space heating processes with two alternative magnitudes of the intermediate value of manipulated variable. New 4-position temperature control schemes are described; and their cycling characteristic is shown for the control of the electric space heating processes. The application of these new techniques to other fields of control, and their limitations, are mentioned.