Flow Control and Unsteady State Analysis on Thermal Performance of Solar Air Collectors

Solar Energy ◽  
2003 ◽  
Author(s):  
Sadasuke Ito ◽  
Minoru Kashima ◽  
Naokatsu Miura
Keyword(s):  
Control System ◽  
Flow Control ◽  
Air Temperature ◽  
Flow Rate ◽  
Thermal Performance ◽  
Unsteady State ◽  
Solar Radiation Intensity ◽  
Flat Plate Collector ◽  
Unsteady State Analysis ◽  
State Analysis

Solar air collectors can be used for heating rooms, drying crops and wood, and heating water. In present studies, first, a flow control system for obtaining a constant temperature at the exit of a flat-plate collector was installed in a hot air supply system and the feasibility of the control system was examined. When the flow temperature was lower than the temperature that was set by a digital indicating controller, the fan power was reduced to decrease the flow rate. When the outlet air temperature was higher than the setting temperature, the flow rate was increased. Consequently, the control system worked well to maintain the exit air temperature. Secondly, an unsteady state analysis was made on thermal performance of the collector. In analysis, flow rate variations over time were given as conditions. Validity of this analysis was checked by experimentation. Analytical results agreed well even when solar radiation intensity, wind speed, or flow rate changed abruptly.

Flow Control and Unsteady-State Analysis on Thermal Performance of Solar Air Collectors

2006 ◽  
Vol 128 (3) ◽  
pp. 354-359 ◽  
Author(s):  
Sadasuke Ito ◽  
Minoru Kashima ◽  
Naokatsu Miura
Keyword(s):  
Control System ◽  
Solar Radiation ◽  
Flow Control ◽  
Flow Rate ◽  
Thermal Performance ◽  
Space Heating ◽  
Outlet Temperature ◽  
Unsteady State ◽  
Collector Efficiency ◽  
Unsteady State Analysis

Promotion of the use of renewable energy, such as solar heat, for space heating and drying crops and wood is desired to prevent global warming. High-temperature collection of heat by air collectors producing as much as 50°C in winter for space heating and about 80°C in summer for exchanging heat to circulating water for hot water supply would be appropriate applications. In this study, first, a flow control system for constant outlet temperature was installed in a hot air supply system to examine the feasibility of the control system. After experiments, it was found that the control system could function satisfactory. Second, an unsteady-state analysis was made to predict the thermal performance of a flat-plate collector under a given condition of variable flow rate. The analytical model became simple by the assumptions that the heat capacity of the air in the collector and heat conduction in the flow direction through the air and the materials of the collector could be neglected. The maximum differences in outlet temperature and collector efficiency for constant flow rate between the analysis and the experiment were 1.8°C and 6% of the collector efficiency, respectively, except in the beginning of experiments. The biggest difference in the collector efficiency was 30% at 3:00 P.M., which occurred at the end of one of the experiments. The analytical results generally agreed well with the experimental results even when the flow rate and solar radiation changed greatly as time went on. Transient effects are important to predict outlet temperature for variable solar radiation intensity, wind speed, and flow rate.

scholarly journals An unsteady state analysis of packed bed reactors for gas-solid reactions.

1984 ◽  
Vol 17 (3) ◽  
pp. 269-275 ◽  
Author(s):  
HEUNG CHUL PARK ◽  
SHOICHI KIMURA ◽  
YUKIO SAKAI ◽  
SETSUJI TONE ◽  
TSUTAO OTAKE
Keyword(s):  
Packed Bed ◽  
Unsteady State ◽  
Packed Bed Reactors ◽  
Unsteady State Analysis ◽  
State Analysis

Thermal Performance Analysis and Optimization of Solar Assisted Heat Pump Water Heater

2014 ◽  
Vol 592-594 ◽  
pp. 2416-2421
Author(s):  
R.N. Kokila ◽  
S. Rajakumar
Keyword(s):  
Mass Flow Rate ◽  
Heat Pump ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Performance ◽  
Optimization Technique ◽  
Direct Expansion ◽  
Water Heater ◽  
Rate Optimization ◽  
Flat Plate Collector

The main objective of this paper is to analyze the thermal performance of direct expansion solar assisted heat pump DX-SAHP(A) by numerical simulation in MATLAB and comparing it with the thermal performance of DX-SAHP(B) which has an optimized collector area and mass flow rate. Optimization is performed for high exergy efficiency using Particle Swarm Optimization (PSO) and Artificial Bee Colony (ABC) optimization technique. The flat plate collector of solar water heater is used as the evaporator with refrigerant (R22).With the optimized value of mass flow rate as 0.055 kg/sec, width as 0.03 m and diameter of riser tubes as 0.021 m the performance of the optimized system has a maximum COP of 6.85 which is greater than the COP of DX-SAHP(A) and the final water temperature of is obtained 100 minutes earlier in the optimized system i.e. DX-SAHP(B) with compressor work less than the system A

Water quality modelling under unsteady state analysis: Strategies for planning and management

2019 ◽  
Vol 239 ◽  
pp. 150-158 ◽  
Author(s):  
Danieli Mara Ferreira ◽  
Cristovão Vicente Scapulatempo Fernandes ◽  
Eloy Kaviski ◽  
Darrell Fontane
Keyword(s):  
Water Quality ◽  
Unsteady State ◽  
Water Quality Modelling ◽  
Planning And Management ◽  
Analysis Strategies ◽  
Unsteady State Analysis ◽  
State Analysis

Modeling and Optimal Control of a Variable-Speed Centrifugal Pump With a Pipeline

2016 ◽  
Author(s):  
Cristian F. Jaimes Saavedra ◽  
Sebastian Roa Prada ◽  
Jessica G. Maradey Lázaro
Keyword(s):  
Mathematical Model ◽  
Control System ◽  
Flow Control ◽  
Flow Rate ◽  
Power Efficiency ◽  
Control Valve ◽  
Operating Point ◽  
Variable Frequency ◽  
Centrifugal Pumps ◽  
Variable Frequency Drive

Pumping processes often require different operating conditions for the same pipeline. The conditions downstream in the pipeline can change in such a way that the pressure at the discharge of the pump may vary, which automatically introduces changes in the flow supplied by the pump into the pipeline due to the head vs flow characteristic curve of the pump. Even under varying pipeline pressure conditions, it may be necessary to keep the flow discharge of the pump constant. The two most commonly used control strategies for flow control with centrifugal pumps are by means of a fixed-speed pump and a control valve at the outlet of the pump, or by means of a variable frequency drive which avoids the need for the control valve. It has been demonstrated that the approach with the fixed-speed pump and the control valve provides poor power efficiency results, so a variable frequency drive is normally the solution of choice in industry applications. The use of a variable frequency drive allows reaching the flow required by the system without changing the physical characteristic of the pump or pipeline, i.e., it is not necessary to shut the system down to replace the impeller of the pump. However, affinity laws of centrifugal pumps dictate that a change in the rotational speed of the impeller shifts the characteristic curves of the pump, not only the flow vs head curve, but also the efficiency curves, among others. Besides, searching for a different operating point by changing the speed of the pump does not necessarily guarantees optimal operating power efficiency. This paper proposes an optimization approach where a compromise is made between flow control and power efficiency by minimizing the error in the flow rate while at the same time maximizing the power efficiency. To accomplish this goal, this paper presents the modeling of the pump and pipeline, and the design of a linear quadratic regulator control for the fluid flow passing through a given pipeline. The fluid under consideration is water. The mathematical model of the overall system is derived by considering the model of an AC motor, the pump and the hydraulic circuit. Then, with the help of the software MATLAB, the controller was designed and implemented with the linearized mathematical model. The actuator of the control system is the variable frequency drive that changes the speed of the impeller to adjust the flow rate to the required operating point under different loading conditions. The results show the behavior of the compensated system with the optimal controller. In practice, the control system must take into account the constraints of the control effort, which means, the frequency of the pump must be kept within safe values to achieve proper functioning of the pumping system.

A Computer-Based Air Flow Control System for Aerosol and Filtration Research

2015 ◽  
Vol 771 ◽  
pp. 137-140 ◽  
Author(s):  
Muhammad Miftahul Munir ◽  
Muhammad Sainal Abidin ◽  
Abdul Rajak ◽  
Khairurrijal
Keyword(s):  
Control System ◽  
Flow Control ◽  
Flow Rate ◽  
Pulse Width Modulation ◽  
Air Flow ◽  
Flow Sensor ◽  
Air Filtration ◽  
Air Filter ◽  
Flow Control System ◽  
Air Flow Control

An airflow control system is one of important parts in the scanning mobility particle sizers system (SMPS) used in the field of aerosol and air filtration. In this paper, the air flow control system that consists of an air filter, a blower, an air flow sensor, a controller, and a computer are reported. A flow rate adjustment was performed by varying the rotation speed of the blower using a pulse width modulation (PWM) technique. The air flow sensor capable of measuring flow rate up to 20 liters / min was used to measure the air flow rate. In order to keep at a certain value of the flow rate, a proportional-integral-derivative (PID) control action was employed in which PID controller were manually tune. The results showed that the desired value of flow rate was quickly achieved with little overshoot was observed in the system output.

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