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Ho-ming Yeh - One of the best experts on this subject based on the ideXlab platform.

  • Effect of Pass Number on Collector Efficiency in Downward-Type Multipass Solar Air Heaters
    2014
    Co-Authors: Ho-ming Yeh
    Abstract:

    The effect of pass number on the Collector Efficiency in downward-type multi-pass solar air heaters has been investigated theoretically. The application of multi-pass operation to solar air heaters actually has two conflict effects. One is the desirable effect of increasing fluid velocity to decrease the heat transfer resistance. The other is the undesirable effect of increasing the hydraulic dissipated power. It is found that considerable improvement in Collector Efficiency is obtainable if the operation is carried out with multi-pass operation, while the undesirable effect is still small and may be ignored. The enhancement increases with increasing pass number, especially for operating at lower air flow rate with higher inlet air temperature.

  • Collector Efficiency in Downward-Type Internal-Recycle Solar Air Heaters with Attached Fins
    Energies, 2013
    Co-Authors: Ho-ming Yeh
    Abstract:

    The internal-recycle operation effect on Collector Efficiency in downward-type rectangular solar air heaters with attached fins is theoretically investigated. It is found that considerable Collector Efficiency is obtainable if the Collector has attached fins and the operation is carried out with internal recycling. The recycling operation increases the fluid velocity to decrease the heat transfer resistance, compensating for the undesirable effect of decreasing the heat transfer driving force (temperature difference) due to remixing. The attached fins provide an enlarged heat transfer area. The order of performance in a device of same size is: double pass with recycle and fins > double pass with recycle but without fins > single pass without recycle and fins.

  • Collector Efficiency in Downward-Type Double-Pass Solar Air Heaters with Attached Fins and Operated by External Recycle
    Energies, 2012
    Co-Authors: Ho-ming Yeh
    Abstract:

    The Collector Efficiency in a downward-type double-pass external-recycle solar air heater with fins attached on the absorbing plate has been investigated theoretically. Considerable improvement in Collector Efficiency is obtainable if the Collector is equipped with fins and the operation is carried out with an external recycle. Due to the recycling, the desirable effect of increasing the heat transfer coefficient compensates for the undesirable effect of decreasing the driving force (temperature difference) of heat transfer, while the attached fins provide an enlarged heat transfer area. The order of performances in the devices of same size is: double pass with recycle and fins > double pass with recycle but without fins > single pass without recycle and fins.

  • Upward-Type Solar Air Heaters with Internal Recycle for Improved Performance
    2012
    Co-Authors: Ho-ming Yeh
    Abstract:

    The influence of internal recycle on the Collector Efficiency in upward-type solar air heaters has been investigated theoretically. The equations for predicting the outlet air temperature and the Collector Efficiency were derived from the energy balances on the absorbing plate and flow air. Considerable improvement in Collector Efficiency is obtainable if the operation is carried out with an internal recycle, where the desirable effect of increase in fluid velocity leading to improved heat transfer, overcomes the undesirable effect of decrease in driving force (temperature difference) of heat transfer due to remixing. The enhancement in Collector Efficiency based on the device of same size without recycle, increases with increasing reflux ratio, especially for operating at lower air flow rate with higher inlet air temperature and radiation incident. It is found that more than 150% of improvement in Collector Efficiency is obtained by recycle operation. Further, the performance in a upward-type solar air heater operated with internal recycle overcomes that in the same-size device operated with external recycle.

  • upward type flat plate solar air heaters attached with fins and operated by an internal recycling for improved performance
    Journal of The Taiwan Institute of Chemical Engineers, 2012
    Co-Authors: Ho-ming Yeh
    Abstract:

    Abstract The effect of internal recycle on the Collector Efficiency in upward-type flat-plate solar air heaters attached with fins has been investigated theoretically. The equations for predicting the outlet air temperature and the Collector Efficiency were derived from the energy balances on the absorbing plate and flow air. Considerable improvement in Collector Efficiency is obtainable if Collector is attached with fins to extend the heat-transfer area, and if the operation is carried out with an internal recycle to increase the fluid velocity, leading to improved heat transfer coefficient. The enhancement in Collector Efficiency increases with increasing reflux ratio, especially for operating at lower air flow rate with higher inlet air temperature. It is found that more than 100% of improvement in Collector Efficiency is obtained by recycling operation. Furthermore, the performance in the device operated with internal recycle overcomes that in the same-size device operated with external recycle.

Tsungching Chen - One of the best experts on this subject based on the ideXlab platform.

  • Collector Efficiency of upward type double pass solar air heaters with fins attached
    International Communications in Heat and Mass Transfer, 2011
    Co-Authors: Ho-ming Yeh, Tsungching Chen
    Abstract:

    The Collector Efficiency of upward-type double-pass flat plate solar air heaters with fins attached and external recycle is investigated theoretically. The double-pass device was constructed by inserting the absorbing plate into the air conduit to divide it into two channels (the upper and lower channels). The double-pass device introduced here was designed for creating a solar Collector with heat transfer area double as well as the extended area of fins between the absorbing plate and heated air. Moreover, the advantage of external recycle application to solar air heaters is the enhancement of forced heat convection strength, resulting in considerable device heat transfer performance improvement. This advantage may compensate for the remixing at the inlet which decreases the heat transfer transfer-driving force decrement (temperature difference).

  • Collector Efficiency of upward-type double-pass solar air heaters with fins attached ☆
    International Communications in Heat and Mass Transfer, 2011
    Co-Authors: Ho-ming Yeh, Tsungching Chen
    Abstract:

    The Collector Efficiency of upward-type double-pass flat plate solar air heaters with fins attached and external recycle is investigated theoretically. The double-pass device was constructed by inserting the absorbing plate into the air conduit to divide it into two channels (the upper and lower channels). The double-pass device introduced here was designed for creating a solar Collector with heat transfer area double as well as the extended area of fins between the absorbing plate and heated air. Moreover, the advantage of external recycle application to solar air heaters is the enhancement of forced heat convection strength, resulting in considerable device heat transfer performance improvement. This advantage may compensate for the remixing at the inlet which decreases the heat transfer transfer-driving force decrement (temperature difference).

  • Collector Efficiency improvement of recyclic double-pass sheet-and-tube solar water heaters with internal fins attached
    Renewable Energy, 2008
    Co-Authors: Tsungching Chen
    Abstract:

    The sheet-and-tube solar water heater is a convenient and common heater to be used as domestic hot water heating. This paper investigates the effects on Collector Efficiency of a double-pass sheet-and-tube solar water heater with fins attached under various arrayed density. In addition, the number of pair ducts and total mass flow rate are taken into account during the calculation procedure. The theoretical prediction shows that the higher Collector Efficiency is obtained under the suitable designing and operating parameters. Considerable improvement in Collector performance is obtained by employing a recyclic operation with fins attached and under various arrayed density, instead of employing a single-pass flat-plate device. The effect of the recycle ratio, arrayed density and number of fins attached on the Collector Efficiency enhancement as well as the power consumption increment has also delineated.

  • Collector Efficiency of Double-Pass Sheet-and-Tube Solar Water Heaters with Internal Fins Attached
    2007
    Co-Authors: Tsungching Chen
    Abstract:

    The moderate temperature solar Collector such as sheet-and-tube water heater is a convenient and simple device to be used in domestic water system. The Collector Efficiency of double-pass sheet-and-tube solar water heaters with attaching internal fins on tube wall and external recycle has been investigated theoretically in this study. The influences of fin attached numbers N(subscript f), recycle ratio R, incident solar radiation I0 and mass flow rate m on the Collector Efficiency were discussed. However, the power consumption increment is a significant magnitude to be taken into account to optimize the Collector Efficiency under the economic sense. The operation of such a double-pass device with external recycle is represented graphically and compared with those in the single-pass device without external recycle under the same working dimensions. There exists an optimal aspect ratio of considering both the Collector Efficiency and power consumption with number of pair ducts as parameter for a specified Collector area. Considerable improvement of Collector Efficiency is obtained by operating such a recyclic device with internal fins attached, under I0=1.0 kJ m^(-2) s^(-1), m=9 kg s^(-1), R=1, n=4 and N(subscript f)=2 instead of using the single-pass device without recycle.

  • the recycle effect on the Collector Efficiency improvement of double pass sheet and tube solar water heaters with external recycle
    Renewable Energy, 2006
    Co-Authors: Chiidong Ho, Tsungching Chen
    Abstract:

    The paper presents a theoretical prediction of the performance of a double-pass sheet-and-tube solar water heater with external recycle and comparison with that of a conventional type Collector. Analytical results show that the recycle effect can effectively enhance the Collector Efficiency compared with that in a single-pass device with the same flow rate. The desirable effect of increasing convective transfer rate and the undesirable effect of reducing heat-transfer driving force are the two conflict effects produced by the recycle operation. It was found that the increment of convective transfer rate by increasing the recycle ratio could generally compensate for the decrement of the temperature difference, leading to improved performance, especially for low flow rate. Also, the Collector Efficiency increases with increasing Collector aspect ratio (i.e. either increasing the tube length or decreasing the number of tube pairs) for a specified Collector area and the distance between tubes.

R Ventas - One of the best experts on this subject based on the ideXlab platform.

  • flat plate thermal solar Collector Efficiency transient behavior under working conditions part i model description and experimental validation
    Applied Thermal Engineering, 2011
    Co-Authors: M C Rodriguezhidalgo, A Lecuona, P Rodriguezaumente, G L Gutierrezurueta, R Ventas
    Abstract:

    Abstract The Efficiency of a solar Collector is a key factor for the performance of thermal facilities. As the weather conditions vary continuously during the day, the instant Collector Efficiency depends not only on the components employed in its construction but also on the actual environmental conditions, the hot water temperature and aging. An experimental research was performed to describe the transient behavior of a flat plate Collector field under outdoor working conditions. A transient Collector model was assembled using thermal resistances and capacitances. Three thermocouples were added to measure the center point temperature of the glass cover, box back surface and absorber plate of one of the Collectors. Using this information, the parameters of a detailed thermal network model were determined. The model useful heat and thermal losses are calculated by applying a dynamic energy balance under the transient regime. The facility is based on a nine-year-old on-campus field with 50 m 2 flat plate solar Collectors, which operated for a domestic hot water (DHW) application. The working parameters were recorded during an entire year for periods of 10 min. The model was experimentally validated by comparing its results to the instant Collector temperatures and heat fluxes that were obtained from the experimental database. Both of the experimental and model results were compared to the direct application of the Collector Efficiency normalization curve (ENC) that was obtained from the EN-12975:2006 test as a reference. Being the operating conditions unlike, differences throughout the day became evident. The influence of several factors is fully described in Part II of this paper.

  • Flat Plate Thermal Solar Collector Efficiency: Transient Behavior Under Working Conditions. Part I: Model Description And Experimental Validation
    Applied Thermal Engineering, 2011
    Co-Authors: M.c Rodríguez-hidalgo, P.a. Rodríguez-aumente, A Lecuona, G.l. Gutiérrez-urueta, R Ventas
    Abstract:

    The Efficiency of a solar Collector is a key factor for the performance of thermal facilities. As the weather conditions vary continuously during the day, the instant Collector Efficiency depends not only on the components employed in its construction but also on the actual environmental conditions, the hot water temperature and aging. An experimental research was performed to describe the transient behavior of a flat plate Collector field under outdoor working conditions.

  • Flat plate thermal solar Collector Efficiency: transient behavior Under working conditions Part Ii: Model Application and design contributions
    Applied Thermal Engineering, 2011
    Co-Authors: M.c Rodríguez-hidalgo, P.a. Rodríguez-aumente, A Lecuona, G.l. Gutiérrez-urueta, R Ventas
    Abstract:

    An experimental research was performed on a solar facility with a nine-year-old, on-campus field with 50m area of flat plate solar Collectors. A transient model was developed, adapted to the characteristics of this facility and experimentally validated as described in Part I of this paper.The Efficiency normalization curve (ENC) operating conditions for the steady-state test are different from the working conditions. Significant differences between the ENC and the model-based predictions were found and quantified.The significance of the transient behavior is compared with the thermal inertia proposed in the EN-12975:2006 standard for the quasi-dynamic test.Using the model capabilities to predict the Collector performance under transient working conditions, the influence of the operating conditions on the Collector Efficiency and on the useful heat produced is studied individually. The relevance of those conditions is ranked as follows: the wind (velocity magnitude and direction) was the most influential, followed by the aging of the Collector surfaces, convective heat losses, thermal inertia and the incident angle of irradiance.

Chiyen Lin - One of the best experts on this subject based on the ideXlab platform.

A Lecuona - One of the best experts on this subject based on the ideXlab platform.

  • flat plate thermal solar Collector Efficiency transient behavior under working conditions part i model description and experimental validation
    Applied Thermal Engineering, 2011
    Co-Authors: M C Rodriguezhidalgo, A Lecuona, P Rodriguezaumente, G L Gutierrezurueta, R Ventas
    Abstract:

    Abstract The Efficiency of a solar Collector is a key factor for the performance of thermal facilities. As the weather conditions vary continuously during the day, the instant Collector Efficiency depends not only on the components employed in its construction but also on the actual environmental conditions, the hot water temperature and aging. An experimental research was performed to describe the transient behavior of a flat plate Collector field under outdoor working conditions. A transient Collector model was assembled using thermal resistances and capacitances. Three thermocouples were added to measure the center point temperature of the glass cover, box back surface and absorber plate of one of the Collectors. Using this information, the parameters of a detailed thermal network model were determined. The model useful heat and thermal losses are calculated by applying a dynamic energy balance under the transient regime. The facility is based on a nine-year-old on-campus field with 50 m 2 flat plate solar Collectors, which operated for a domestic hot water (DHW) application. The working parameters were recorded during an entire year for periods of 10 min. The model was experimentally validated by comparing its results to the instant Collector temperatures and heat fluxes that were obtained from the experimental database. Both of the experimental and model results were compared to the direct application of the Collector Efficiency normalization curve (ENC) that was obtained from the EN-12975:2006 test as a reference. Being the operating conditions unlike, differences throughout the day became evident. The influence of several factors is fully described in Part II of this paper.

  • Flat Plate Thermal Solar Collector Efficiency: Transient Behavior Under Working Conditions. Part I: Model Description And Experimental Validation
    Applied Thermal Engineering, 2011
    Co-Authors: M.c Rodríguez-hidalgo, P.a. Rodríguez-aumente, A Lecuona, G.l. Gutiérrez-urueta, R Ventas
    Abstract:

    The Efficiency of a solar Collector is a key factor for the performance of thermal facilities. As the weather conditions vary continuously during the day, the instant Collector Efficiency depends not only on the components employed in its construction but also on the actual environmental conditions, the hot water temperature and aging. An experimental research was performed to describe the transient behavior of a flat plate Collector field under outdoor working conditions.

  • Flat plate thermal solar Collector Efficiency: transient behavior Under working conditions Part Ii: Model Application and design contributions
    Applied Thermal Engineering, 2011
    Co-Authors: M.c Rodríguez-hidalgo, P.a. Rodríguez-aumente, A Lecuona, G.l. Gutiérrez-urueta, R Ventas
    Abstract:

    An experimental research was performed on a solar facility with a nine-year-old, on-campus field with 50m area of flat plate solar Collectors. A transient model was developed, adapted to the characteristics of this facility and experimentally validated as described in Part I of this paper.The Efficiency normalization curve (ENC) operating conditions for the steady-state test are different from the working conditions. Significant differences between the ENC and the model-based predictions were found and quantified.The significance of the transient behavior is compared with the thermal inertia proposed in the EN-12975:2006 standard for the quasi-dynamic test.Using the model capabilities to predict the Collector performance under transient working conditions, the influence of the operating conditions on the Collector Efficiency and on the useful heat produced is studied individually. The relevance of those conditions is ranked as follows: the wind (velocity magnitude and direction) was the most influential, followed by the aging of the Collector surfaces, convective heat losses, thermal inertia and the incident angle of irradiance.