Thermal Performance Analysis Of Solar Air Heaters

1984 ◽  
pp. 1-15
Author(s):  
Mohamad Jamil ◽  
Prof. Madya Amer Nordin Darus
Keyword(s):  
Performance Analysis ◽  
Low Temperature ◽  
Flat Plate ◽  
Flow Rate ◽  
Thermal Performance ◽  
Air Flow ◽  
Design Parameters ◽  
Air Flow Rate ◽  
Governing Equations ◽  
Radiation Exchange

A computer routine to calculate the thermal performance of several different low temperature types of flat-plate air heaters is to be discussed. Analysis of each type is also described. The programme accepts as input real or simulated flux, collector geometry, air flow rate and enviromental data. It computes temperatures and extracts energy as a function of time of the day. The programme evaluates radiation,convection, conduction and wind losses, and the radiation exchange with the enviromental conditions.The procedure used in the derivation of the governing equations is also described. The prediction of performance provided by this programme is particularly useful in comparing performances of different collectors and for studying a specific collector's performance with changes in enviroment and design parameters which can be controlled to some extent by the designer.

Optimization of oxygen transfer in clean water by fine bubble diffused air system and separate mixing in aeration ditches

1998 ◽  
Vol 38 (3) ◽  
pp. 35-42 ◽  
Author(s):  
G. Déronzier ◽  
Ph. Duchène ◽  
A. Héduit
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Oxygen Transfer ◽  
Contact Time ◽  
Air Flow ◽  
Interfacial Area ◽  
Design Parameters ◽  
Air Bubbles ◽  
Air Flow Rate ◽  
Fine Bubble

The influence of design parameters on the transfer of oxygen was studied in different ring ditches equipped with fine bubble membrane air diffusers and separate mixing. The results produced evidence that the oxygen transfer efficiency (OTE) decreases when the air flow rate per diffuser increases. OTE increases asymptotically with the horizontal water flow (50% for velocity up to 0.5 m/sec). It increases also when the diffuser modules are brought closer together. Theoretical analysis enabled ranking of the impact of the design parameters on which the oxygen transfer is dependent, namely the interfacial area (a) and the oxygen transfer coefficient (Kl). The increase in the air flow rate per diffuser essentially reduces the interfacial area by an increase in the diameter of the initial air bubbles and by a reduction of the contact time due to an acceleration of the “spiral flows” (vertical rotation of water flow). The horizontal rotation of water increases the interfacial area most probably by decreasing the diameter of the initial air bubbles and by a lengthening of the contact time resulting from a reduction in the large spiral flows. Bringing the diffuser modules closer together makes longer the contact time by a reduction in the large spiral flows.

scholarly journals Air preheating potential with high Opaque Ventilated Façade under natural and forced convection

2021 ◽  
Vol 2069 (1) ◽  
pp. 012023
Author(s):  
T Colinart ◽  
H Noel ◽  
M Batard ◽  
A Fuentes ◽  
A Magueresse ◽  
...  
Keyword(s):  
Forced Convection ◽  
Flow Rate ◽  
Natural Ventilation ◽  
Positive Impact ◽  
Air Flow ◽  
Thermal Flux ◽  
Building Envelope ◽  
Design Parameters ◽  
Building Energy Efficiency ◽  
Air Flow Rate

Abstract Opaque ventilated façades (OVF) are increasingly used in building envelope because of their positive impact on building energy efficiency. Usually, air flow is driven by natural ventilation. Recently, there were some attempts to drive air flow mechanically to preheat or precool air in combination with HVAC, Heat pump or Latent Heat Thermal Energy Storage (LHTES) systems. In this framework, an experimental real-scale module of an OVF was built (1.9 m width and 3.5 m height). In this study, OVF is tested during autumn under natural and under forced convection by means of ventilator placed at cavity outlet. Inlet air flowrate are changed from day to day or during the day. For each test, temperature, air velocity, air flow rate and thermal flux are monitored at different locations of OVF. Their analysis shows that collector efficiency and amount of collected energy depend mainly on cavity air flow rate. The measurements are compared to simulation results obtained from two thermal models describing OVF: Trnsys Type 1230 and home-developed pseudo 2D. A good agreement is found for air temperature at cavity outlet while differences are observed in opaque layers due to modelling assumptions. Last, sensitivity analysis on two design parameters is carried out.

scholarly journals Empirical Thermal Performance Investigation of a Compact Lithium Ion Battery Module under Forced Convection Cooling

2020 ◽  
Vol 10 (11) ◽  
pp. 3732
Author(s):  
Akinlabi A. A. Hakeem ◽  
Davut Solyali
Keyword(s):  
Flow Rate ◽  
Thermal Performance ◽  
Air Flow ◽  
Lithium Ion ◽  
Operating Conditions ◽  
Battery Pack ◽  
Performance Criteria ◽  
Maximum Temperature ◽  
Air Flow Rate ◽  
Worst Case

Lithium ion batteries (LiBs) are considered one of the most suitable power options for electric vehicle (EV) drivetrains, known for having low self-discharging properties which hence provide a long life-cycle operation. To obtain maximum power output from LiBs, it is necessary to critically monitor operating conditions which affect their performance and life span. This paper investigates the thermal performance of a battery thermal management system (BTMS) for a battery pack housing 100 NCR18650 lithium ion cells. Maximum cell temperature (Tmax) and maximum temperature difference (ΔTmax) between cells were the performance criteria for the battery pack. The battery pack is investigated for three levels of air flow rate combined with two current rate using a full factorial Design of Experiment (DoE) method. A worst case scenario of cell Tmax averaged at 36.1 °C was recorded during a 0.75 C charge experiment and 37.5 °C during a 0.75 C discharge under a 1.4 m/s flow rate. While a 54.28% reduction in ΔTmax between the cells was achieved by increasing the air flow rate in the 0.75 C charge experiment from 1.4 m/s to 3.4 m/s. Conclusively, increasing BTMS performance with increasing air flow rate was a common trend observed in the experimental data after analyzing various experiment results.

HIGH-SPEED IMAGING FOR AN OPTICALLY ACCESSIBLE ROTATING DETONATION ENGINE

2020 ◽  
Author(s):  
Yuhui Wang ◽  
◽  
Jialing Le ◽  
Keyword(s):  
Low Temperature ◽  
Flow Rate ◽  
High Speed ◽  
Equivalence Ratio ◽  
Air Flow ◽  
Detonation Waves ◽  
Outer Diameter ◽  
Air Flow Rate ◽  
High Speed Imaging ◽  
Rotating Detonation

Nonpremixed rotating detonation waves (RDWs) for ethylene or hydrogen and air sources at room temperatures 283-284 K were obtained in the same hollow combustor. The combustor was optically accessible by embedded a piece of quartz glass in the combustor wall. The hollow combustor channel here had an outer diameter 100 mm. Fuel and air were injected into the combustor from 150 cylindrical orifices of a diameter 0.8 mm axially and a circular channel with a width 1 mm radially, respectively. The detonation speeds for ethylene and air were 1562 or 1389 m/s for the air flow rate 642.35 g/s at an equivalence ratio 0.78. The detonation speed for hydrogen and air were 2013 m/s for the air flow rate 327.73 g/s at an equivalence ratio 1.24. Hydrogen operation was more stable than ethylene operation in the condition of low temperature gas sources. High-speed images showed RDW structures were changeful and unstable. Low-temperature regions could intrude into and break the detonation wave.

scholarly journals First and Second Law Evaluation of Multipass Flat-Plate Solar Air Collector and Optimization Using Preference Selection Index Method

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Nguyen Thanh Luan ◽  
Nguyen Minh Phu
Keyword(s):  
Flat Plate ◽  
Flow Rate ◽  
Air Flow ◽  
Selection Index ◽  
Exergy Efficiency ◽  
Air Flow Rate ◽  
Double Pass ◽  
Index Method ◽  
Glass Cover ◽  
Effective Efficiency

In this paper, different flow configurations of multipass flat-plate air collectors are explored. Multiple passes are formed from glass cover, absorber plate, and back plate. Five types of air collectors were analysed and optimized with respect to maximum efficiencies and minimum cost. The analytical prediction of the heat exchanger, pressure loss, and efficiencies was presented. The effects of mass flow rate from 0.01 to 0.02 kg/s, air channel depth from 15 to 30 mm, and collector length from 1.5 to 2.5 m on different configurations were examined and compared. The results of the parametric study show that the triple-pass type has the greatest efficiency, whereas the smallest efficiency is of the single-pass type. Among double-pass types, the type with two glass covers and natural convection heat transfer achieved the highest effective and exergy efficiencies due to a reduction in the top loss. Double-pass type with single glass cover is not recommended from both energy and exergy standpoints. As the collector length increases, the effective efficiency decreases, but the exergy efficiency increases. The exergy performance of the triple-pass type can reach up to 5% at the air flow rate of 0.005 kg/s. Finally, multiobjective optimization using the preference selection index method is conducted with three targets including effective efficiency, exergy efficiency, and number of plates. Optimal results show that the triple-pass type with the lowest air flow rate and the longest length is the best. The effective and exergy efficiencies for the best case were found to be about 52.1% and 4.7%, respectively. However, this type with the highest flow rate and the shortest length is the worst.

Performance Analysis of a Reheat Cycle Gas Turbine Based on Measured Data

2007 ◽  
Author(s):  
Soo Hyoung Yoon ◽  
Dae Hwan Jeong ◽  
Jong Joon Lee ◽  
Tong Seop Kim
Keyword(s):  
Performance Analysis ◽  
Gas Turbine ◽  
Flow Rate ◽  
Air Flow ◽  
Combined Cycle ◽  
Inlet Guide Vane ◽  
Air Flow Rate ◽  
Operating Condition ◽  
Estimated Parameters ◽  
Condition Change

This study evaluated component characteristics of the reheat cycle gas turbine in a combined cycle power plant. High pressure ratio, sequential combustion, large amount of cooling flow and full utilization of the inlet guide vane distinguishes the engine from simple cycle engines. Considering the detailed engine configuration, performance analysis using an inverse calculation, based on measured performance data, has been carried out to estimate the component characteristic parameters that closely match the measured performance parameters. The measured parameters are power, fuel flow rates of two combustors, and temperatures and pressures at compressor discharge, exits of both high and low pressure turbines. The estimated parameters from the analysis include not only the compressor and turbine efficiencies but also the inlet air flow rate. The analysis has been performed for a wide operation range in terms of ambient temperature and load. Not only the absolute value of the inlet air flow rate but also its variation with the operating condition change correspond very well with the reference data from the manufacturer. The compressor and turbine efficiencies at each full load condition and their variations with the operating condition change were examined. The sensitivity of the estimated parameters to the uncertainties of the measured parameters has also been investigated.

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