scholarly journals Money versus time: evaluation of flow control in terms of energy consumption and convenience

2012 ◽  
Vol 700 ◽  
pp. 406-418 ◽  
Author(s):  
Bettina Frohnapfel ◽  
Yosuke Hasegawa ◽  
Maurizio Quadrio
Keyword(s):  
Energy Consumption ◽  
Drag Reduction ◽  
Flow Control ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Transport Sector ◽  
Pumping Power ◽  
Total Energy Consumption ◽  
Practical Applications

AbstractFlow control with the goal of reducing the skin-friction drag on the fluid–solid interface is an active fundamental research area, motivated by its potential for significant energy savings and reduced emissions in the transport sector. Customarily, the performance of drag reduction techniques in internal flows is evaluated under two alternative flow conditions, i.e. at constant mass flow rate or constant pressure gradient. Successful control leads to reduction of drag and pumping power within the former approach, whereas the latter leads to an increase of the mass flow rate and pumping power. In practical applications, however, money and time define the flow control challenge: a compromise between the energy expenditure (money) and the corresponding convenience (flow rate) achieved with that amount of energy has to be reached so as to accomplish a goal which in general depends on the specific application. Based on this idea, we derive two dimensionless parameters which quantify the total energy consumption and the required time (convenience) for transporting a given volume of fluid through a given duct. Performances of existing drag-reduction strategies as well as the influence of wall roughness are re-evaluated within the present framework; how to achieve the (application-dependent) optimum balance between energy consumption and convenience is addressed. It is also shown that these considerations can be extended to external flows.

scholarly journals Design and Fabrication of a Novel Window-Type Convection Device

2020 ◽  
Vol 11 (1) ◽  
pp. 267
Author(s):  
Han-Tang Lin ◽  
Yunn-Horng Guu ◽  
Wei-Hsuan Hsu
Keyword(s):  
Energy Consumption ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Energy Demand ◽  
Air Entrainment ◽  
Wind Speeds ◽  
Digit Series ◽  
Slit Size ◽  
Deflector Plate

Global warming, climate change, and ever-increasing energy demand are among the pressing challenges currently facing humanity. Particularly, indoor air conditioning, a major source of energy consumption, requires immediate improvement to prevent energy crises. In this study, various airfoil profiles were applied to create a window-type convection device that entrains air to improve convection between indoor and outdoor airflows and adjust the indoor temperature. How the geometric structure of the convection device affects its air entrainment performance was investigated on the basis of various airfoil profiles and outlet slit sizes of the airflow multiplier. The airfoil profiles were designed according to the 4-digit series developed by the National Advisory Committee for Aeronautics. The results revealed that airfoil thickness, airfoil camber, and air outlet slit size affected the mass flow rate of the convection device. Overall, the mass flow rate at the outlet of the convection device was more than 10 times greater than at the inlet, demonstrating the potential of the device to improve air convection. To validate these simulated results, the wind-deflector plate was processed using the NACA4424 airfoil with a 1.2 mm slit, and various operating voltages were applied to the convection device to measure the resulting wind speeds and calculate the corresponding mass flow rates. The experimental and simulated results were similar, with a mean error of <7%, indicating that the airfoil-shaped wind-deflector plate substantially improved air entrainment of the convection device to the goal of reduced energy consumption and carbon emissions.

scholarly journals Implementation of a Floating Head Pressure Condensation Control to Reduce Electrical Energy Consumption in an Industrial Refrigeration System

2021 ◽  
Vol 11 (24) ◽  
pp. 11923
Author(s):  
Fábio Luiz da Costa Carrir ◽  
Cesare Biserni ◽  
Danilo Barreto Aguiar ◽  
Elizaldo Domingues dos Santos ◽  
Ivoni Carlos Acunha Júnior
Keyword(s):  
Energy Consumption ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Electric Energy ◽  
Electrical Energy ◽  
Industrial Facilities ◽  
Improve Energy Efficiency ◽  
Electric Energy Consumption ◽  
Industrial Refrigeration

The growing global demand for energy and the costly taxes on electric energy demonstrate the importance of seeking new techniques to improve energy efficiency in industrial facilities. Refrigeration units demand a large amount of electricity due to the high power needs of the components of the system. One strategy to reduce the electric energy consumption in these facilities is pressure condensation control. The objective here was to develop a logical control model where the physical quantities in the thermodynamic process can be monitored and used to determine the optimum point of the condensation pressure and the mass flow rate of the air in the evaporative condenser. The algorithm developed was validated through experiments and was posteriorly implemented in an ammonia industrial system of refrigeration over a period of sixteen months (480 days). The results showed that the operation of the evaporative condenser with a controlled air mass flow rate by logical modeling achieved a reduction of 7.5% in the consumption of electric energy, leading to a significant reduction in the operational cost of the refrigeration plant.

scholarly journals A Critical Review on Thermo-Hydraulic Performance of Wire Screen Matrix Packed Solar Air Heaters

2021 ◽  
Author(s):  
Prashant Verma ◽  
Abhishek Saxena ◽  
L. Varshney
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Hydraulic Performance ◽  
Major Influence ◽  
Pumping Power ◽  
Bed Porosity ◽  
Wire Screen ◽  
The Impact

Solar air heaters (SAHs) have an important role in applications such as space heating and industrial drying worldwide. The packing of SAH bed not only increases the heat transfer area but also increases the pumping power losses thereby limiting the thermo-hydraulic performance. In the present study, efforts have been made for a critical assessment of the literature dealing with the impact of collector bed and operating parameters over thermal and thermo-hydraulic performance for different configurations of wire screen matrix packed SAH. The porosity of bed and mass flow rate of the air have a major influence on the thermo-hydraulic performance of wire screen matrix packed SAH. It is found that the enhancement in the volumetric heat transfer coefficient due to a decrease in bed porosity is obtained at the expense of increase in pumping power which ultimately affects the thermo-hydraulic performance of wire screen matrix packed SAH. In general it is observed that porosity is an important parameter that affects the thermo-hydraulic performance. It is seen that matrix having porosity 0.937 yields thermo-hydraulic performance of 68% at mass flow rate 0.023 kg/s where as for the same mass flow rate porosity of 0.887 results thermo-hydraulic performance of only 42%.

Performance Evaluation of Concentrated Photovoltaic System Using a Microchannel Heat Sink

2016 ◽  
Author(s):  
Ali Radwan ◽  
Mahmoud Ahmed ◽  
Shinichi Ookawara
Keyword(s):  
Solar Cell ◽  
Mass Flow Rate ◽  
Double Layer ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Sink ◽  
Single Layer ◽  
Microchannel Heat Sink ◽  
Pumping Power ◽  
Cell Temperature

The high incident heat flux on the concentrated photovoltaic (CPV) system causes a significant increase in the cell temperature and thus reduces the system efficiency. Therefore, using an efficient cooling technique is of great importance for those systems. In the present study, a new technology for concentrated photovoltaic systems is introduced using a truncated-double layer microchannel heat sink. A comprehensive three-dimensional thermo-fluid model for the photovoltaic layers integrated with a microchannel heat sink was developed. The proposed model was simulated numerically to estimate the solar cell temperature, temperature uniformity, cooling system pumping power, electrical efficiency and thermal efficiency of the CPV system. The numerical results were validated with the available experimental, analytical and numerical results in the literature. In the designed heat sink, various design parameters are investigated such as the truncation length, cooling mass flow rate, concentration ratio, and converging width ratio of the flow channel. Results indicate that increasing the truncated length leads to an increase of solar cell temperature at a constant coolant mass flow rate. The cell temperature varies between 80.1°C and 146.5°C as the truncation length ratio increases from 0 (i.e. single layer microchannel) to 1 respectively at a concentration ratio (CR) of 40 and a cooling mass flow rate (ṁ) of 26.6 g/min. Using the double layer microchannel reduces the consumed pumping power at the same total mass flow rate compared to the single layer microchannel. The Double layer configuration with a truncation length ratio (l/lsc) equal to unity achieves a lower pumping power and solar cell temperature uniformity in comparison to the single layer microchannel.

A Brief Model to Evaluate the Behaviour of R134a/R1234yf Mixtures on a Reciprocating Compressor

2015 ◽  
Author(s):  
J. M. Barroso-Maldonado ◽  
J. M. Belman-Flores ◽  
C. Rubio-Maya
Keyword(s):  
Energy Consumption ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Energy Savings ◽  
Energy Performance ◽  
Error Band ◽  
Discharge Temperature ◽  
Mass Fractions ◽  
Discharge Pressure

Transitioning from R134a refrigerant to a low global warming potential (GWP) refrigerant is a current issue of global importance. Although any refrigerant still has set; there are a few options to replace it such as the R1234yf. In this paper is presented a semi-empirical model to assess the energy performance of mixtures with R134a and its possible substitute R1234yf. The inputs variables to the computational model are: suction conditions (pressure and temperature), discharge pressure and rotation speed. With these variables the model must compute the following parameters: mass flow rate, discharge temperature and energy consumption. The model is validated with data obtained from an experimental facility; calculations are obtained within a relative error band of ±10% for mass flow rate and energy consumption, and an error of ±1 K for discharge temperature. Finally, the model is carried out to an energy simulation in order to predict the behavior of different mass fractions of R1234yf. Energy savings are found when R1234yf mass fraction is reduced from 1 to 0.9. Knowing that the mixture with y=0.9 may be used as its GWP is 150.

The effect of water mass flow rate and pressure on specific energy consumption and aquades production using throttling process method

2020 ◽  
Author(s):  
Muhammad Irfan Dzaky ◽  
Engkos Achmad Kosasih ◽  
Ahmad Zikri ◽  
Salsabil Dwikusuma Prasetyo ◽  
Muhammad Badra Shidqi ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Specific Energy ◽  
Water Mass ◽  
Specific Energy Consumption ◽  
Effect Of Water ◽  
Water Mass Flow Rate ◽  
Process Method

Experimental Study of Suction Flow Control Effectiveness in a Serpentine Intake

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
M. C. Keerthi ◽  
Abhijit Kushari ◽  
Valliammai Somasundaram
Keyword(s):  
Flow Control ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Surface Pressure ◽  
Total Pressure ◽  
Engine Performance ◽  
Secondary Flows ◽  
Detailed Measurement ◽  
Pressure Distributions

The intakes of modern aircraft are subjected to ever-increasing demands in their performance. Particularly, they are expected to carry out diffusion with the highest isentropic efficiency while subjected to aggressive geometry requirements arising from stealth considerations. To avoid a penalty in engine performance, the flow through intake needs to be controlled using various methods of flow control. In this study, a serpentine intake is studied experimentally and its performance compared with and without boundary layer suction. The performance parameters used are nondimensional total pressure loss coefficient and standard total pressure distortion descriptors. The effect is observed on surface pressure distributions, and inferences are made regarding separation location and extent. A detailed measurement at the exit plane shows flow structures that draw attention to secondary flows within the duct. Suction is applied at three different locations, spanning different number of ports along each location, comprising of ten unique configurations. The mass flow rate of suction employed ranges from 1.1% to 6.7% of mass flow rate at the inlet of the intake. The effect is seen on exit total pressure recovery as well as circumferential and radial distortion parameters. This is examined in the context of the location of the suction ports and amount of suction mass flow, by the deviation in surface pressure distributions, as well as the separation characteristics from the baseline case. The results show that applying suction far upstream of the separation point together with a modest amount of suction downstream results in the best performance.

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