Improvement of Outlet Nozzle Shape for Pressure-Loss Reduction in Air Conditioner

2016 ◽  
Author(s):  
Daiwa Sato ◽  
Taku Iwase ◽  
Hideshi Obara ◽  
Naoyuki Fushimi
Keyword(s):  
Heat Exchanger ◽  
Response Surface ◽  
Cross Section ◽  
Flow Separation ◽  
Pressure Loss ◽  
Air Flow ◽  
Power Reduction ◽  
Air Conditioner ◽  
Outlet Nozzle ◽  
Nozzle Shape

A reduction of fan power is required to develop high efficiency air conditioner. Fan-power reduction is achieved by reducing of the pressure loss of flow channels and/or improving the efficiency of a fan. An indoor unit of the air conditioner in the present study is installed on a ceiling in a room. The indoor unit consists of a centrifugal fan, a heat exchanger, an air inlet and 4 air-outlet nozzles. One of the areas of the highest pressure-loss in the indoor unit is around the air-outlet nozzles since the cross-section of the flow channel in the air-outlet nozzles is smaller than those in other areas. In addition, the path of air flow after passing through the heat exchanger is sharply turned downward by a cabinet wall of the indoor unit. The air flow separates in the air-outlet nozzles when the air flow gets over a drain pan which receives water condensed on the surface of the heat exchanger. As a result, the effective cross-section of the air-outlet nozzles is further reduced due to the flow separation. This is main cause of the pressure-loss in the air-outlet nozzles. The optimum nozzle shape to suppress flow separation in air-outlet nozzles of the indoor unit of an air conditioner was determined. An edge, shaped on the wall of the drain pan, minimized the flow separation by corresponding to the location between the edge and the attachment point of the flow separation. The location of the edge is defined by two parameters, and the influence of the parameters on reduction of fan power was determined by using Computational Fluid Dynamics (CFD). A CFD model of a whole indoor unit (including fan, heat exchanger, air-outlet nozzles) was applied to accurately predict fan power for different locations of the edge. Furthermore, the flow separation in the air-outlet nozzle was visualized on the basis of the CFD results. To obtain the appropriate combination of parameters to suppress the flow separation, a response surface based on the CFD results and approximate values given by a Kriging-based method, was used. The Kriging-based model is one of the response-surface methods and is characterized by approximating a nonlinear function based on Bayesian probabilistic estimation. The response surface provided the area containing the appropriate parameters for reducing fan power (“parameter area”, hereafter). The parameter area of fan-power reduction on the response surface was found. The CFD results confirm that the flow separation corresponds to the edge location given by this parameter area and that the edge minimizes the flow separation. To experimentally verify the effect of the edge on fan-power reduction, four points in the parameter area for fan-power reduction were selected, and four nozzle shapes with these parameters were prototyped. It was found that fan power was reduced (at most) by 9.9% by the optimized nozzles shapes in comparison with the current shape of air-outlet nozzles.

scholarly journals Comparison of a Novel Polymeric Hollow Fiber Heat Exchanger and a Commercially Available Metal Automotive Radiator

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1175
Author(s):  
Tereza Kroulíková ◽  
Tereza Kůdelová ◽  
Erik Bartuli ◽  
Jan Vančura ◽  
Ilya Astrouski
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Hollow Fiber ◽  
Pressure Loss ◽  
Air Flow ◽  
Performance Parameters ◽  
University Of Technology ◽  
Flat Tubes ◽  
And Performance ◽  
Louvered Fins

A novel heat exchanger for automotive applications developed by the Heat Transfer and Fluid Flow Laboratory at the Brno University of Technology, Czech Republic, is compared with a conventional commercially available metal radiator. The heat transfer surface of this heat exchanger is composed of polymeric hollow fibers made from polyamide 612 by DuPont (Zytel LC6159). The cross-section of the polymeric radiator is identical to the aluminum radiator (louvered fins on flat tubes) in a Skoda Octavia and measures 720 × 480 mm. The goal of the study is to compare the functionality and performance parameters of both radiators based on the results of tests in a calibrated air wind tunnel. During testing, both heat exchangers were tested in conventional conditions used for car radiators with different air flow and coolant (50% ethylene glycol) rates. The polymeric hollow fiber heat exchanger demonstrated about 20% higher thermal performance for the same air flow. The efficiency of the polymeric radiator was in the range 80–93% and the efficiency of the aluminum radiator was in the range 64–84%. The polymeric radiator is 30% lighter than its conventional metal competitor. Both tested radiators had very similar pressure loss on the liquid side, but the polymeric radiator featured higher air pressure loss.

Nucleation and subsequent cavitation in a hydraulic oil poppet valve

2010 ◽  
Vol 224 (4) ◽  
pp. 947-958 ◽  
Author(s):  
S Washio ◽  
S Kikui ◽  
S Takahashi
Keyword(s):  
Cross Section ◽  
Relative Motion ◽  
Flow Separation ◽  
Pressure Loss ◽  
Flow Pulsation ◽  
Valve Seat ◽  
Poppet Valve ◽  
Induced Flow ◽  
Cavitation Nuclei ◽  
Liquid Flows

If bubble nuclei are the cause of cavitation, how are they initially produced? According to what Washio et al. have found out so far, there are two possible ways for cavitation nuclei to be generated in liquid flows: separation of flow and a relative motion between solids contacting in liquid. The present article intends to reinforce that assertion by observing the cavitation occurring in an oil hydraulic poppet valve. At a certain flowrate, a microscopic cavity suddenly emerged on the valve seat where the flow separated. As the flowrate increased, the cavity developed extending circumferentially on the seat and discharged bubbles by splitting. A collision of the poppet with the valve seat also caused the generation of a cavity. As the poppet was away from the seat after the collision, the cavity shrunk leaving behind a bubble. Cavities generated on the seat by flow separation regularly repeated a process of growth and shrinkage accompanied by bubble discharge, which induced flow pulsation and consequently vibration of the poppet supported by a spring as well. Moreover, these cavities brought about so-called ‘choking’ in the poppet—seat constriction and acted to increase the pressure loss there by narrowing its cross-section.

Analysis of Turbulent Flow in 180° Turning Ducts With and Without Guide Vanes

2007 ◽  
Author(s):  
Jiang Luo ◽  
Eli H. Razinsky
Keyword(s):  
Turbulent Flows ◽  
Cross Section ◽  
Flow Separation ◽  
Pressure Loss ◽  
Numerical Study ◽  
Guide Vane ◽  
Outer Wall ◽  
Loss Reduction ◽  
Guide Vanes ◽  
Curvature Effects

This paper presents a numerical study of the turbulent flows through a number of 2-D and 3-D 180° U-ducts, with and without guide vanes, using the Reynolds-averaged Navier-Stokes method. Computations have been first carried out for a 2-D U-duct flow (W/H = 1.0) with four turbulence models (V2F, k-ε, SST and Reynolds stress). The models’ capability for streamline curvature effects on turbulence and separation has been assessed, using flow and turbulence data. The effects of adding a guide vane inside the bend have been analyzed, to reduce/avoid flow separation. Three vanes with different radial locations have been studied, and the mechanism for pressure loss reduction has been examined. Analyses have been performed for turbulent flows in 3-D U-ducts with square cross-section and sharp 180° turning (W/D = 0.2), similar to the U-bends in typical turbine blade cooling passages. The predictions are compared with the data of outer wall pressure. The effects of the guide vane and outer-wall shape on the flow separation, secondary-flow vortices and pressure loss have been evaluated. The combined vane and uniform cross-section area provide a large benefit for the flow distribution and pressure loss reduction.

Analysis of Turbulent Flow in 180 deg Turning Ducts With and Without Guide Vanes

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Jiang Luo ◽  
Eli H. Razinsky
Keyword(s):  
Turbulent Flows ◽  
Cross Section ◽  
Flow Separation ◽  
Pressure Loss ◽  
Numerical Study ◽  
Guide Vane ◽  
Outer Wall ◽  
Duct Flow ◽  
Guide Vanes ◽  
Curvature Effects

This paper presents a numerical study of the turbulent flows through a number of 2D and 3D 180 deg U-ducts, with and without guide vanes, using the Reynolds-averaged Navier–Stokes method. Computations have been first carried out for a 2D U-duct flow (W/H=1.0) with four turbulence models (V2F, k-ε, shear stress transport (SST), and Reynolds stress). The models’ capability for predicting streamline curvature effects on turbulence and separation has been assessed, using flow and turbulence data. The effects of adding a guide vane inside the bend have been analyzed to reduce/avoid flow separation. Three vanes with different radial locations have been studied, and the mechanism for pressure loss reduction has been examined. Analyses have been performed for turbulent flows in 3D U-ducts with square cross section and sharp 180 deg turning (W/D=0.2), similar to the U-bends in typical turbine blade cooling passages. The predictions are compared with the data of outer-wall pressure. The effects of the guide vane and outer-wall shape on the flow separation, secondary-flow vortices, and pressure loss have been evaluated. The combined vane and uniform cross section area are found to improve the flow distribution and reduce the pressure loss significantly.

Parametric analysis, response surface, sensitivity analysis, and optimization of a novel spiral-double ground heat exchanger

2021 ◽  
Vol 240 ◽  
pp. 114251
Author(s):  
Ahmed A. Serageldin ◽  
Ali Radwan ◽  
Takao Katsura ◽  
Yoshitaka Sakata ◽  
Shigeyuki Nagasaka ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Heat Exchanger ◽  
Response Surface ◽  
Parametric Analysis ◽  
Ground Heat Exchanger ◽  
Surface Sensitivity
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