Fan Control Research Articles

Noise and Noise Control of Fan for Air Conditioning System

Noise and Noise Control of Fan for Air Conditioning System

Continuous Commissioning Energy Management Case Study of an Outpatient Clinic Building

ABSTRACT Continuous commissioning (CC) utilizes the HVAC system retrofit with system optimization theory and advanced technologies in a federal outpatient clinic building. The case study building has a basement and a first floor with patient rooms, offices, and a pharmacy. The HVAC system consists of two single-duct VAV air handling units (AHUs), 112 single-duct pneumatic controlled pressure independent terminal boxes, and associated hot/chilled water booster pumps. Both AHUs share one heat recovery heat exchanger. Major retrofit efforts include installing a VFD on the exhaust fan and reheat hot water pump, and installing fan airflow stations (FAS) and pump waterflow stations (PWS). This article presents optimal control strategies, which include outside air intake control, heat recovery from exhaust air control, supply fan control integrated with FAS, return fan control, optimal control for terminal boxes, and hot water and chilled water pump speed control. The measured daily utility data after CC shows t...

Incorporating fan control into air-conditioning systems to improve energy efficiency and transient response

Modern air-conditioners frequently incorporate variable-speed compressors and variable-opening expansion valves with feedback control to improve performance and power efficiency. Because making the fan speeds adjustable adds flexibility to the control design and thus can lead to further improvements in performance and efficiency, this paper proposes two control algorithms, respectively, incorporating the outdoor fan and the indoor fan as the additional control inputs for air-conditioning systems. Both of the control algorithms are designed based on a low-order, linear model obtained from system identification. The first algorithm, which modulates the outdoor fan speed, can reduce the steady state power consumption if the temperature difference between the condenser and the outdoor environment is controlled properly. The second algorithm, which adds one more degree of freedom to control by modulating the indoor fan speed, can improve the transient response because actuator saturations become less likely to occur. The two control algorithms are implemented on a split-type residential air-conditioner and their respective performance is validated experimentally.

Practical near hover flight control of a ducted fan (SLADe)

The development of a near hover flight control system for an electrically powered, coaxial, counter-rotating ducted fan aircraft (SLADe—surface launched aerial decoy) is presented. The control and estimation algorithms are designed to operate with low-cost sensors, be computationally efficient, robust and easily adaptable from flight test data. Successive loop closure is employed in the controller design with feedback signals from linear decoupled estimators. Simulation results verify the controller functionality and show that the decoupled estimators perform well near hover when compared to a coupled nonlinear 16 state Kalman filter. Flight test results are presented that verify the practical success of the autopilot.

Automotive Fan Control with Smart Power Switch [From Mind to Market

This article presents a fan control unit requiring 30 A motor currents up to 20 kHz PWM. The smart integrated circuit (IC) used here includes a self-protected high-side switch with 4 mOmega RDSON, all digital control from a microcontroller, and extended diagnostics. High-current switching at high frequency generates electromagnetic interference (EMI) and power losses. Corner rounding and slew rates were optimized to reduce EMI filter size on the module. The power QFN (PQFN) package, half the size of the equivalent conventional package, helps to evacuate high power dissipation during switching. A smart power switch, combined with a 16-b microcontroller (MCU) and the control area network (CAN) communication protocol, provides an embedded solution, bringing cost savings on the system.

Energy savings from inverter drives in the efficient building

As our energy reserves dwindle while costs continue to rise and as the spectre of climate change looms ever larger, it becomes ever more imperative to take action on energy savings. Recent legislation is now making the route of no-action impossible. Danfoss' John Martin, strategic business area manager, HVAC put the case forward for intelligent inverter speed control of fans and pumps in buildings.

Application of Innovative Technologies for a Continuous Commissioning Case Study

ABSTRACT This article demonstrates the implementation of innovative technologies during continuous commissioning® (CC) practices to improve building operations and reduce energy costs. A 46-year-old typical commercial building with a floor area of about 216,000 square feet was used as a case study building. The HVAC systems were upgraded and retrofitted in 2000. Variable frequency drives (VFDs) were installed for most of the fans and pumps. This CC project involved very minor HVAC retrofits and control upgrades. The new technologies include the fan airflow station (FAS) technology for building pressure control and supply fan control, and a recently developed pump water flow station for secondary pump control. The results show that these technologies improve building operation/maintenance and significantly reduce energy costs. The monthly average electricity savings for HVAC systems is 64 percent, and the average gas savings is 49 percent.

Optimizing condenser fan control for air-cooled centrifugal chillers

The current design and operation of air-cooled condensers can cause a significant decrease in chiller performance under part load conditions. This paper demonstrates optimal condenser fan control to improve the coefficient of performance (COP) of air-cooled chillers. This control involves identifying the optimum set point of condensing temperature with the optimized power relationships of the compressors and condenser fans and enhancing the airflow and heat transfer area of the condensers. An example application of this control for an air-cooled centrifugal chiller indicated that the COP could increase by 11.4–237.2%, depending on the operating conditions. Such the increase of the COP results in a reduction of up to 14.1 kWh/m 2, or 27.3% in the annual electricity consumption per unit A/C floor area of chillers, given that the chillers serve an office building requiring an annual cooling energy per unit A/C floor area of 173.3 kWh/m 2. The simulation results of this study will give HVAC engineers a better understanding of how to optimize the design and operation of air-cooled chillers.

Energy saving in agricultural buildings through fan motor control by variable frequency drives

A comparison was conducted between ON–OFF and variable frequency drive (VFD) systems to control ventilation fans of greenhouses and poultry houses. The study aimed to determine the effect of each system on the energy consumption and resulting microclimate within the houses. The experiments were carried out in a commercial-size greenhouse in which pepper was grown and in commercial poultry houses. Reducing the fan speed with the VFD system resulted in reductions in the airflow rate through the houses and energy consumption, the latter being much more significant. The study showed that VFD control can reduce electricity consumption compared with ON–OFF operation. In the present study, the average energy consumption with the VFD control system was about 0.64 and 0.75 of that with an ON–OFF system in the greenhouse and poultry houses, respectively. The average greenhouse daily air temperatures and humidity ratios obtained with each control system between 07:00 and 18:00 were nearly equal. The results obtained in the greenhouse further showed that the VFD system has a greater potential than the ON–OFF, to reduce the range of amplitude variations in the air temperature and humidity ratio within the greenhouse. The average air temperatures over day and night, in the poultry houses, with each control system were nearly equal. The relative humidity, however, was slightly lower with VFD than with ON–OFF. Reductions in the range of amplitude variations of the air temperature and humidity were also observed in the poultry houses.

Modelling of a condenser-fan control for an air-cooled centrifugal chiller

There is a lack of detailed experimental and simulation studies on air-cooled centrifugal chillers. This paper investigates how to optimize the control of condenser fans within the chillers to maximize their coefficients of performance (COPs). A thermodynamic model for the chillers was developed and used to analyse the steady-state COP under various load and ambient conditions. An algorithm is introduced to compute the number of staged condenser fans based on settings of the condensing pressure and outdoor temperature. The model was validated using the experimental data and performance data of an existing chiller running under various operating conditions. It is found that the best strategy for switching condenser fans is to vary their rotating speed by the use of a set point of the condensing temperature, which is adjusted in response to the chiller load and condenser air-inlet temperature. The results of this paper provide an important insight into how to increase the COPs of air-cooled chillers.

Part load performance of air-cooled centrifugal chillers with variable speed condenser fan control

Air-cooled centrifugal chillers are commonly used in commercial buildings but their performance analysis is lacking. This paper investigates the part load performance of the chillers via a thermodynamic model. The model was validated using a wide range of operating data from an existing chiller with specific settings of outdoor temperature and condensing pressure in controlling the condensing temperature. The validated model was developed specifically to ascertain the maximum coefficient of performance of chiller (COP) together with the strategy for optimizing the condensing temperature under various operating conditions. It is found that the highest COP occurs at a part load ratio (PLR) of 0.71–0.84, depending on the outdoor temperature and the control of condensing temperature, rather than at full load. Yet the chillers operating at such part load conditions will cause extra energy used for the early staging of chilled water pumps. To minimize the overall chiller plant energy consumption, it is still preferable to implement chiller sequencing based on the full load condition than on the aforementioned PLRs. The results of this paper present criteria for implementing low-energy strategies for operating air-cooled chillers satisfying a given building cooling load profile.

A Smart Translation From the Response of the Piezoelectric Transducer to a Real-Time Ventilating Signal for the Release of Cooking Fumes

Although the amount of cooking fumes can be estimated based on the output of the piezoelectric transducer, a proper translation from the response of the transducer to the exhaust rate remains to be implemented. In this paper, a smart translation method is used to generate a ventilating signal for the release of cooking fumes based on the output of a piezoelectric transducer. The start and end states of the fume release were computed according to the temporal variation of the output of the piezoelectric transducer, as determined with four successive samples. These detected states were mapped to a 1-bit digital ventilating signal, which then controlled the exhaust fan. Results from a demonstrated range hood system showed that the proposed method enhances the detection of cooking fumes and provides an effective control of the exhaust fan

Field Implementation and Model Validation of a Model-Based Fan and Burner Control Strategy for the In-Bin Drying and Conditioning of Corn

A new model-based self-adapting variable heat (SAVH) fan and burner control strategy for the in-bin drying and conditioning of corn was successfully implemented in three field experiments during the 2004 drying season. These experiments were carried out in three different locations throughout Indiana, in bins with different capacities (from 57 to 431 tonnes) and with two different corn types (yellow dent and white corn). One continuous natural air (CNA) experiment was also carried out drying yellow dent corn in a 57-tonne bin. The SAVH control strategy was able to successfully dry wet corn to a final moisture content (MC) close to 15%, with a relatively uniform final MC in the entire grain mass. Compared to the CNA strategy, the SAVH control strategy successfully avoided the overdrying of the grain under the same weather conditions.

The crucial role of inverter drives in the energy-efficient building

As our energy reserves dwindle, as the spectre of climate change looms ever larger and as energy cost continue to rise, it becomes ever more imperative to take action on energy savings. Recent legislation is now making the route of no-action impossible. Danfoss' John Martin , Strategic Business Area Manager, HVAC put the case forward for intelligent inverter speed control of fans and pumps in buildings.

Low-temperature aeration to control Indianmeal moth, Plodia interpunctella (Hübner), in stored grain in twelve locations in the United States: a simulation study

Aeration management strategies were developed to control cold-acclimated and diapausing Indianmeal moth, Plodia interpunctella (Hübner), larvae in grain bins during winter in north- and east-central regions of the US. The application in this study focuses on corn because it is the dominant crop in these regions, but we believe that the analyses can be applied to other grains as well. Contour maps for hours below −10 °C for the months of December, January, and February were developed to help effective planning and management of aeration to control overwintering stored-grain insects. Two cumulative lethality index (CLI) models were developed to estimate mortality of laboratory-reared (diapausing without cold-acclimation) and field-collected (cold-acclimated, and diapausing with cold-acclimation) P. interpunctella larvae under changing temperature conditions. The CLI models were used for evaluating aeration management strategies. Simulation studies were conducted using 30 years of weather data for 12 locations in north- and east-central regions of the US to evaluate different aeration management strategies for controlling P. interpunctella larvae. For each strategy, temperatures of headspace air and grain in the top meter of the grain mass were simulated using an existing model for the period of December–February. The tested management strategies included no aeration, continuous aeration, and intermittent aeration by controlling fan operation. During aeration, air was pulled from the headspace downward through the grain with an airflow rate of 0.11 m 3/min-t (0.1 cfm/bu). Simulation results indicated that a fan control strategy that turned the aeration fan on when the grain temperature at 0.4-m depth was greater than the headspace-air temperature was the best strategy for managing P. interpunctella larvae in all tested locations. For this strategy, the CLI model indicated that 100% mortality of P. interpunctella larvae could be achieved at a grain depth of 0.4 m from the top grain surface in all locations. For this strategy, the aeration fan operated about 10% of the time from December to February. The average cost of electrical energy required for aeration fan operation with this strategy for all locations was 1.3 ¢/t (0.033 ¢/bu) based on an electrical energy cost of 7 ¢/kWh.

Control of the road tunnel CO density by a feedforward algorithm

For a long road tunnel, a tunnel ventilation system may be used in order to reduce the pollution below the required level. To control the tunnel pollution, a closed loop control algorithm may be used. A feedforward prediction algorithm and a cascade control algorithm were developed to regulate the CO level in a tunnel. The feedforward prediction algorithm composed of a traffic estimation algorithm and a CO density prediction algorithm, and the cascade control algorithm composed of a jet fan control algorithm and an air velocity setpoint algorithm. The verification of control algorithms was carried out by dynamic models developed from actual tunnel data. Simulation results showed that control algorithms developed for this research may be effective for the control of the tunnel ventilation system. (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. Reprinted with permission from Elsevier.

SIMULINK-FEMLAB Integrated Dynamic Simulation Model for a PEM Fuel Cell System

The necessity for reliable simulation models, able to support the fuel cell systems development activity, has increased continuously during the last years. The present work proposes a model which integrates the finite element method in a dynamic simulation, in order to achieve higher accuracy and the possibility to investigate the influence of various parameters on the fuel cell dynamics. The model is implemented using MATLAB/SIMULINK and consists of two interacting main subsystems that calculates the fuel cell power response and the stack thermal behavior. The first simulates the mass transport and electrochemical phenomena using a model implemented in FEMLAB, and considers as input parameters the stack geometry, reactants pressure, flow rate and composition, and the stack average temperature. The last parameter is also evaluated by the second model, implemented also in FEMLAB, which considers the stack geometry, cooling air flow rate and ambient temperature. Both models were validated using the experimental data acquired on a Ballard Nexa 1.5kWe proton exchange membrane (PEM) system. The results prove that integrated model simulates with accuracy the dynamics of the proton exchange membrane fuel cell type (PEMFC) system and the interaction between the stack and the auxiliaries. The proposed model was used as a predictive tool for two situations. In the first simulation, with a relative fast dynamic, the model demonstrates that the cooling fan control strategy is essential for transient conditions characterized by a significant load decreasing. In the second, the model estimates the variation of the PEMFC main parameters on a 24h cycle, confirming its reliability.

Fan control for a ceiling mount flat TV monitor

The thermal design of a fan control circuit for use in a ceiling mount Flat TV monitor is discussed. The objective of using the fan control is to lower the noise from the Flat TV monitor to a level that is suitable for living room use. Furthermore, the circuit is used as a protective measure for overly high temperatures. From an analysis of the requirements it follows that the fan control circuit needs a certain amount of hysteresis to remain stable. Technical and end-customer requirements are translated into so-called robust design requirements for the fan control circuit. Robust requirements take the effect of component tolerances on the functioning of the circuit into account. The spread in several circuit designs is evaluated as a function of component tolerances, using Monte Carlo simulations. Finally, the best design is chosen and the circuit is tested in the climatic room. The final test shows that the design is successful: no oscillations occur.

Performance of Model-based Predictive Control of the Ventilation Rate with Axial Fans

A new algorithm for ventilation rate control in mechanically ventilated buildings was developed and evaluated on a laboratory test installation. It was demonstrated that the current problems with traditional control of axial fans, such as instability due to dynamic wind actions, could be overcome by using a model-based predictive control (MBPC) algorithm. In the laboratory test installation, the performance of the MBPC algorithm was compared to the performance of a traditional proportional, integral, derivative (PID) controller in an airflow range from 1000 to 5000 m3/h (20–100% of fan capacity) and in a normal pressure range from 0 to 60 Pa. The accuracy and the stability of the ventilation rate control and the energy consumption were studied for both control algorithms. It was concluded that the main advantage of a MBPC algorithm over a PID controller lies in its stability in a wider range of the ventilation rates and pressure differences due to an automatic adaptation of the control parameters. The PID algorithm with fixed settings did not generate a stable control of the ventilation rate when the target value deviated more than 500 m3/h (16% of centre capacity) from the ventilation rate that it was optimised for, whereas the MBPC controller remained stable throughout the complete working range of the fan.

Air quality and ventilation fan control based on aerosol measurement in the bi-directional undersea Bømlafjord tunnel

Aerosol, NO and CO concentration, temperature, air humidity, air flow and number of running ventilation fans were measured by continuous analysers every minute for a whole week for six different one-week periods spread over ten months in 2001 and 2002 at measuring stations in the 7860 m long tunnel. The ventilation control system was mainly based on aerosol measurements taken by optical scatter sensors. The ventilation turned out to be satisfactory according to Norwegian air quality standards for road tunnels; however, there was some uncertainty concerning the NO2 levels. The air humidity and temperature inside the tunnel were highly influenced by the outside metrological conditions. Statistical models for NO concentration were developed and tested; correlations between predicted and measured NO were 0.81 for a partial least squares regression (PLS1) model based on CO and aerosol, and 0.77 for a linear regression model based only on aerosol. Hence, the ventilation control system should not solely be based on aerosol measurements. Since NO2 is the hazardous polluter, modelling NO2 concentration rather than NO should be preferred in any further optimising of the ventilation control.