The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform

Saffa Riffat - One of the best experts on this subject based on the ideXlab platform.

  • Numerical determination of energy Losses at duct junctions
    Applied Energy, 2000
    Co-Authors: Guohui Gan, Saffa Riffat
    Abstract:

    The Pressure-Loss Coefficient for a duct junction of square cross-section was determined using computational fluid dynamics (CFD). The predicted junction Pressure-Loss Coefficient for combining flows was generally in good agreement with experimental data from the literature. The junction Pressure-Loss Coefficient was associated with the flow from the side branch to the duct carrying the total flow.

  • CFD modelling of Pressure Loss across tube bundles of a heat exchanger for closed-wet cooling towers
    International journal of ambient energy, 2000
    Co-Authors: Guohui Gan, Saffa Riffat, L. Shao
    Abstract:

    SYNOPSIS Computation Fluid Dynamics (CFD) is applied to predicting the Pressure Loss Coefficient of tube bundles for closed-wet cooling towers. The prediction involves the single-phase air flow and two-phase flow of gas and water droplets. The accuracy of CFD modelling of the Pressure Loss Coefficient is assessed for single-phase air flow over closely-spaced tube bundles for a range of flow velocities applied in closed-wet cooling towers. The Pressure Loss Coefficient for both single- and two-phase flow over tube bundles with large transverse pitches is then determined by CFD modelling. It is shown that the Pressure Loss Coefficient decreases with transverse pitch but increases with water-to-air mass flow ratio.

  • Determination of energy Loss characteristics of dampers
    International Journal of Energy Research, 1999
    Co-Authors: Guohui Gan, Saffa Riffat
    Abstract:

    The Pressure Loss Coefficient of a flat-plate damper for ducted air systems has been determined using computational fluid dynamics (CFD) and experimental measurement. The constant-injection tracer-gas technique and a pitot tube were used to measure mean air velocity in a square duct fitted with a damper. Pressure distribution along the duct was measured using static Pressure tappings. The Pressure Loss Coefficient was calculated from the measured Pressure Loss and mean velocity for the duct fitting. CFD was used to predict airflow and Pressure distribution in the duct. The predicted Pressure Loss Coefficient was generally in good agreement with experimental results. The Pressure Loss Coefficient for the damper was found to be sensitive to the clearance between the fitting and duct as well as the degree of damper opening. Copyright © 1999 John Wiley & Sons, Ltd.

  • Determination of effectiveness of heat-pipe heat recovery for naturally-ventilated buildings
    Applied Thermal Engineering, 1998
    Co-Authors: Saffa Riffat
    Abstract:

    Abstract The performance of three types of heat-pipe heat recovery unit for naturally-ventilated buildings was tested in a two-zone chamber with a horizontal partition. Air velocity was found to have a significant influence on the effectiveness of heat recovery. The effectiveness decreased with increasing air velocity. The effectiveness was also affected by the shape of fins and pipe arrangement. The Pressure Loss characteristics of heat recovery units were determined using computational fluid dynamics (CFD). It was found that at low velocities for natural ventilation the Pressure Loss Coefficient decreased with increasing air velocity but the total Pressure Loss increased with the velocity.

  • Pressure Loss characteristics of orifice and perforated plates
    Experimental Thermal and Fluid Science, 1997
    Co-Authors: Saffa Riffat
    Abstract:

    A study was conducted on the Pressure Loss characteristics of square-edged orifice and perforated plates. Tests were carried out to determine the Pressure Loss Coefficient for thin plates in a square duct for a range of Reynolds numbers. Computational fluid dynamics (CFD) was used to predict the Loss Coefficient, and the result was compared with experimental measurement. The effect of plate thickness on the Loss Coefficient for the orifice plate was studied using CFD.

Junshan Wang - One of the best experts on this subject based on the ideXlab platform.

  • effects of Pressure Loss Coefficients of heat exchanger on thermal performance of the dry cooling tower
    Energy Procedia, 2017
    Co-Authors: Fengqi Si, Xuebo Li, Junshan Wang
    Abstract:

    Abstract Crosswind deteriorates thermal performance of the natural draft dry cooling tower (NDDCT) mainly due to the unfavorable Pressure distribution at tower entrance. Thus, effects of air cooled heat exchanger with various Pressure Loss Coefficients are investigated with numerical simulation. The vortex inside the tower would cut down air inflow of heat exchanger of sideward and leeward parts. A quite large exponent of Pressure Loss Coefficient expression of heat exchanger contributes to reduce heat transfer unevenness among cooling deltas, and would generate a small enhancement for the overall thermal performance of the tower.

Jayathi Y Murthy - One of the best experts on this subject based on the ideXlab platform.

  • low reynolds number flow through nozzle diffuser elements in valveless micropumps
    Sensors and Actuators A-physical, 2004
    Co-Authors: Vishal Singhal, Suresh V Garimella, Jayathi Y Murthy
    Abstract:

    Flow characteristics of low Reynolds number laminar flow through gradually expanding conical and planar diffusers were investigated. Such diffusers are used in valveless micropumps to effect flow rectification and thus lead to pumping action in one preferential direction. Four different types of diffuser flows are considered: fully developed and thin inlet boundary layer flows through conical and planar diffusers. The results from the numerical analysis have been quantified in terms of Pressure Loss Coefficient. The variation of Pressure Loss Coefficient with diffuser angle is presented for Reynolds numbers of 200, 500 and 1000. The Pressure Loss Coefficients have been used to calculate the diffuser efficiency for two different types of nozzle-diffuser elements. The general trend of variation of Pressure Loss Coefficient with diffuser angle was found to be similar to that for high Reynolds number turbulent flow. However, unlike at high Reynolds numbers, Pressure Loss Coefficients at low Reynolds numbers vary significantly with Reynolds number. It was also observed that trends of variation in the Pressure Loss Coefficient with Reynolds number are different for small and large diffuser angles. Also, at low Reynolds numbers, the Pressure Loss Coefficients for a thin inlet boundary layer are not always smaller than those for fully developed inlet boundary layer, in contrast to the behavior for high Reynolds number flows. Contrary to past claims, flow rectification is shown to be indeed possible for laminar flows. The two different types of nozzle-diffuser elements considered led to pumping action in opposite directions. Further, it was observed that flow rectification properties of both kinds of nozzle-diffuser elements improved with increasing Reynolds number.

Predrag Stojan Hrnjak - One of the best experts on this subject based on the ideXlab platform.

  • Single phase Pressure drop in round cylindrical headers of parallel flow MCHXs
    2014
    Co-Authors: Tao Ren, Amir Chavoshi, Guoliang Ding, Predrag Stojan Hrnjak
    Abstract:

    This paper presents the investigation of the Pressure drop in headers and development of correlation for Pressure Loss Coefficient for single phase flow through round cylindrical headers of parallel MCHXs. The working fluid was compressed air flowing through header with 1 - 20 m/s based on smallest cross section while the velocity through micro-channels was in the range 6 - 30 m/s. The experimental results indicate that the Pressure Loss Coefficient of inlet header is a linear function of the ratio of velocities through micro-channel tube and header, except for the first two micro-channel tubes; the Pressure Loss Coefficient of outlet header is a quadratic function of the ratio of velocities through micro-channel tube and header, and decreases as the velocities through upstream micro-channel tubes increase. Correlations for predicting Pressure drop of inlet header and outlet header are developed and agree for 98% of experimental data is within a ±15 Pa.

  • Pressure drop in round cylindrical headers of parallel flow MCHXs: Pressure Loss Coefficients for single phase flow
    International Journal of Refrigeration-revue Internationale Du Froid, 2014
    Co-Authors: Tao Ren, Predrag Stojan Hrnjak
    Abstract:

    Abstract This paper presents the investigation of the Pressure drop in headers and development of correlation for Pressure Loss Coefficient for single phase flow through round cylindrical headers of parallel MCHXs. The working fluid was compressed air flowing through header with 1–20 m s −1 based on smallest cross section while the velocity through microchannels was in the range 6–30 m s −1 . The experimental results indicate that the Pressure Loss Coefficient of inlet header is a linear function of the ratio of velocities through microchannel tube and header, except for the first two microchannel tubes; the Pressure Loss Coefficient of outlet header is a quadratic function of the ratio of velocities through microchannel tube and header, and decreases as the velocities through upstream microchannel tubes increase. Correlations for predicting Pressure drop of inlet header and outlet header are developed and agreement for 98% of experimental data is within a ±15 Pa.

  • Pressure drop in D shaped cylindrical headers of parallel flow MCHXs: Pressure Loss Coefficients for single phase flow
    Applied Thermal Engineering, 2014
    Co-Authors: Tao Ren, Predrag Stojan Hrnjak
    Abstract:

    Abstract This paper presents the investigation of the Pressure drop in headers and development of the correlation for Pressure Loss Coefficient for single phase flow through D shaped cylindrical headers of parallel MCHXs. D shaped headers are becoming more popular compared to conventional round cylindrical types due to reduction in charge and Pressure drop, despite complexity at difficulties in handling higher Pressures. The working fluid was compressed air flowing through header with 1–20 m/s based on smallest cross section while the velocity through microchannels was in the range 4–25 m/s. The experimental results indicate that the Pressure Loss Coefficient of inlet header is a linear function of the ratio of velocities through microchannel tube and header, except for the first two microchannel tubes; the Pressure Loss Coefficient of outlet header is a quadratic function of the ratio of velocities through microchannel tube and header, and decreases as the velocities through upstream microchannel tubes increase. Correlations for predicting Pressure drop of inlet header and outlet header are developed and agreement for 98% of experimental data is within ±15 Pa.

Fengqi Si - One of the best experts on this subject based on the ideXlab platform.

  • effects of Pressure Loss Coefficients of heat exchanger on thermal performance of the dry cooling tower
    Energy Procedia, 2017
    Co-Authors: Fengqi Si, Xuebo Li, Junshan Wang
    Abstract:

    Abstract Crosswind deteriorates thermal performance of the natural draft dry cooling tower (NDDCT) mainly due to the unfavorable Pressure distribution at tower entrance. Thus, effects of air cooled heat exchanger with various Pressure Loss Coefficients are investigated with numerical simulation. The vortex inside the tower would cut down air inflow of heat exchanger of sideward and leeward parts. A quite large exponent of Pressure Loss Coefficient expression of heat exchanger contributes to reduce heat transfer unevenness among cooling deltas, and would generate a small enhancement for the overall thermal performance of the tower.