Air-Fin Coil Performance as a Function of Tube Layout

An attempt is made in this study to analyze complex configurations of cross flow heat exchangers. There are 3 objectives to be achieved in this study. Firstly, in order to obtain effectiveness value for complex configurations of cross flow heat exchangers, general methods for solving simultaneous equations by using MATLAB software will be developed. Secondly, this study aims to perform analysis for chosen heat exchanger configurations. Lastly, the result will be validated by using comparison analysis with well–established EVAP COND software. For co-flow, counter flow and simple cross flow arrangement, the value of effectiveness is given in the literature. Meanwhile, for more complex cross-flow heat exchanger, it is difficult to solve for the value of effectiveness since it involve simultaneous equations. The equations must be solved for each individual layout and cannot be generalized for all configurations. Therefore effectiveness for various complex configurations is yet to be published in any literature. A finned tube evaporator model is used by using EVAPCOND software. The modelling scheme is “tube-by-tube” and allows for specification of complex refrigerant circuits. It capability was to simulate refrigerant distribution in the refrigerant circuit. Simulation models that account for refrigerant circuit architecture are better equipped for accurately predicting heat exchanger performance. This is because the refrigerant path (co flow, cross flow, cross counter flow and cross co flow) through the heat exchanger can have a significant effect on heat exchanger performance. Several complex air finned coil heat exchangers has been analysed by using Chain Rule method in finding the value of effectiveness

Air-Fin Coil Performance as a Function of Tube Layout

An attempt is made in this study to analyze complex configurations of cross flow heat exchangers. There are 3 objectives to be achieved in this study. Firstly, in order to obtain effectiveness value for complex configurations of cross flow heat exchangers, general methods for solving simultaneous equations by using MATLAB software will be developed. Secondly, this study aims to perform analysis for chosen heat exchanger configurations. Lastly, the result will be validated by using comparison analysis with well–established EVAP COND software. For co-flow, counter flow and simple cross flow arrangement, the value of effectiveness is given in the literature. Meanwhile, for more complex cross-flow heat exchanger, it is difficult to solve for the value of effectiveness since it involve simultaneous equations. The equations must be solved for each individual layout and cannot be generalized for all configurations. Therefore effectiveness for various complex configurations is yet to be published in any literature. A finned tube evaporator model is used by using EVAPCOND software. The modelling scheme is “tube-by-tube” and allows for specification of complex refrigerant circuits. It capability was to simulate refrigerant distribution in the refrigerant circuit. Simulation models that account for refrigerant circuit architecture are better equipped for accurately predicting heat exchanger performance. This is because the refrigerant path (co flow, cross flow, cross counter flow and cross co flow) through the heat exchanger can have a significant effect on heat exchanger performance. Several complex air finned coil heat exchangers has been analysed by using Chain Rule method in finding the value of effectiveness

Combustion characteristics of biogas flame from Palm Oil Mill Effluent (POME) at variable equivalence ratio

The use of different fuels in unmodified engines requires a thorough understanding of the change of combustion characteristics that are introduced by the different fuel. In the present study, the combustion characteristics of biogas at different equivalence ratio through numerical analysis are studied. A non-premixed flame is simulated based on a lab scaled burner with methane as a fuel for validation purpose. The turbulent non-premixed combustion simulation was performed by usin

Multi-angle swirling fluidized bed drying of stingless bees pot-pollen

Pot-pollen is another stingless bee product, a mixture of pollen, honey, and bee enzyme stored in cerumen pots. Pot-pollen is protein rich and have therapeutic properties. However, they contain high moisture rendering them susceptible to microbial and fungi growth which will lead to spoilage without proper storage. Conventional methods to remove moisture includes sun drying, oven drying, and food dehydrators. However, they can be unhygienic, reduce pot-pollen quality, and lengthy drying time. Swirling fluidized bed dryer (SFBD) is a promising alternative as they have rapid drying time without damaging the nutrients. The addition of multi-angle swirling distributor (MASD) has the potential to improve drying performance without additional energy input. The current study aim to investigate the drying performance of swirling fluidized bed dryer with multi-angle distributor. Raw pot-pollen is dried in a lab scale SFBD at 3.0 m/s using single angle and multi-angle swirling distributors, 6767, 6730, and 6745. The results shown that the multi-angle swirling distributors 6730 and 6745 improved the drying performance of SFBD, by 17.1 % and 6.5 %, respectively. The best drying performance is shown by the 6730 distributor. Thus, multi-angle SFBD is able to rapidly dry the heat-sensitive stingless bee pot-pollen and represented significant improvement from single angle SFBD

Drying performance of piper nigrum in a swirling fluidized bed dryer: An experimental study

Sun drying is widely used in drying agricultural products such as piper nigrum because of its ability to dry a high volume in one batch. However, this conventional method of drying has many disadvantages, especially on the hygienic issue. This study investigates the drying performance of piper nigrum by using conventional sun drying and a new dryer called Swirling Fluidized Bed Dryer. Swirling fluidized bed dryer is operated using two inclination angles of air distributors, namely 45°, 67° and one perforated plate distributor. The drying performance is accessed in terms of drying time and moisture content reduction at three different operating temperatures. The results show that the drying time of piper nigrum using a swirling fluidized bed dryer is reduced as compared to conventional sun drying. Besides, the drying performance between different distributors in swirling fluidized bed shows that the moisture content reduction of piper nigrum using 45° angle of air distributor shows the most reduction compared to 67° angle distributor and followed by the perforated distributor. In conclusion, results show that the drying of piper nigrum in a swirling fluidized bed operated with 45° inclination angle of the distributor at high operating temperature gives the best performance

Hydrodynamics investigations of kaffir lime leaves drying in a swirling solar drying chamber with inclined slotted angle air distributor

The present work aims to investigate the behavior of drying kaffir lime leaves in a swirling solar drying chamber (S-SDC) fitted with an inclined slotted angle air distributor. A distributor plated with inclined slotted angle was located at the air inlet at the bottom of the chamber. Experimental and numerical methods have been applied to analyze the efficiency of developed S-SDC assisted solar drying system based on the moisture content (MC), moisture content ratio (MR) and drying rate (DR) were examined. The experimental results showed that the S-SDC can reduce the moisture content of kaffir lime leaves more rapidly than a conventional solar drying chamber (CSDC). The S-SDC gave a higher DR and decreased drying time compared to that of C-SDC. The results also indicated that operation at higher air velocities resulted in a greater DR, especially at the beginning stage of the drying process. For the S-SDC, the reduced of MC, MR and DR at a high air velocity (v = 2.0 m/s) was better than at low air velocities (v = 0.5 and 1.0 m/s). Drying chamber efficiency is also observed at a higher air velocity of 2 m/s for both SSDC and CSDC. In addition, obtained experimental findings are in line with numerical results. The outcomes of this study present the potential of using the S-SDC compared to the C-SDC to be used in drying crops

Performance characteristics of air distributor designs in a fluidized bed

High pressure drop across the distributor for fluidizing air supply to the bed is one of major draw backs of the current air distributor designs. Besides, the mechanically assisted agitator and rotating distributor were installed to improve mixing inside the bed. Therefore, in order to minimize the cost of using high capacity blower as well as to reduce the energy, viable design of air distributors that can contribute to low pressure drop and improved particulate mixing in fluidized bed are essential. The present study aims to numerically and experimentally investigate the flow patterns and hydrodynamics in a fluidized bed operated with different configuration of distributors. The optimum mode of operation and the parameters that contribute to low pressure drop and improved particulate mixing in a fluidized bed is identified. The commonly used distributor designs are modified to suit in the fluidization operation with a low pressure blower. A fluidized bed column of 108 mm in diameter with six different air distributors; conventional perforated plate, multi-nozzles, and newly proposed slotted distributors with inclination angles of 90°, 67°, 45° and 30° are used in the simulations and experiment. In this study, 177 jim and 520 jim alumina and, 543 jim and 756 Pm river sands categorized in Geldart Group B particle are used to investigate the hydrodynamics of gas-solid fluidization. The numerical simulations by using the Re-Normalisation Group (RNG) k-s turbulent model show that when the inflow direction of the fluidizing air is inclined at 67°, 45° and 30° through the distributor slots, air flow pattern inside the bed is shown to produce swirling motion in a vicinity of the distributors. Also, the induced swirling air motion eliminates major dead zone regions. Experiment with bed materials show that at aspect ratio H/D0.4 and 0.5, the bed pressure drop is observed to be the lowest in the fluidized beds operated by 90° distributor and highest by the perforated plate distributor. Considerable increment of bed pressure drop is observed by 67°, 45° and 30° distributors as compared to 900. Interestingly, the minimum fluidization velocity is observed to take place promptly in a fluidized bed operated by 301 and 670 distributors. In other words, the fluidization occurred at low air flow rate in a bed operated by these inclined distributors. A continuous swirling bottom layer and a vigorously bubbling top layer are visible in a fluidized bed operated by 67°, 45° and 30° distributors. The degree of mixing is found to be influenced by the size and shape of bed materials in which intense mixing is observed by the fine bed and more stable mixing is spotted by the coarser bed. For all distributors, the distributor to bed pressure drop ratio is found to fall within the range of uniform operation of fluidization; except for the operation by using perforated plate distributor. The performance of the distributors is further assessed in terms of temperature distribution in the bubbling fluidization regime by using 67° and perforated distributors. Finally, a new pressure drop correlation is developed based on the Forchheimer-Ergun equation that takes into account the design parameter of the distributors with different inclination angles and different types of bed materials. The constants obtained through the regression analysis provided excellent predictions to the experimental data with maximum average error of 9%. In conclusion, a novel inclined 67° distributor is proposed as a new distributor for FBC due to lower pressure drop operation and improved particulate mixing as compared to conventional type distributors. This research finding could contribute to higher application of the fluidized bed technology, particularly in Malaysia where fluidized bed technology is still not popularly used in power generation plant using biomass as solid fuel

Studies on the residence time distribution of solids in a swirling fluidized bed

The Multi-Parameter Two-Layer (MPTL) mathematical model was developed in this work specifically to model the Residence Time Distribution (RTD) of particles in a continuous system of swirling fluidized bed reactor.The model consists of two parallel layers.The top layer is a stirred tanks-in-series model and represents the conventional fluidized bed. Meanwhile,the bottom layer obeys the general recycle model and represents the swirling motion at the bottom layer of the bed.The Laplace transformation and convolution integral techniques are used to derive explicit expressions for the RTD functions of the stirred tanks-in-series model and general recycle model.The proposed model has six independent parameters-recycle fraction(P),recycle layer flow rate fraction (w),recycle layer volume fraction(Yr)'number of tanks in the main flow line of the recycle layer(n 1 ), line (n 2 )and number of tanks in the top layer number of tanks in the recycle (n o ).The RTD experiments were conducted at different particle sizes and bed weights.The bed material used in the experimental work is spherical plastic beads with a diameter and = 3.85mm.During hydrodynamics study,it is found that bed pressure drop AP,increases with air velocity and bed weight. Besides, the smaller bed particle gives a higher pressure drop for a given bed.The effects of parameters on the RTD function E(0) are studied and the model is shown to be highly versatile and capable of representing widely different mixing conditions depending on the system variables.By best-fitting of the model response to the experimental data,the model parameters can be evaluated.The experimental result of solid RTD shows that the bed performance varies from one-layer to two-layer bed as the bed weight increased.One layer bed can be modeled by having number of stirred tanks n2 = 4. P, w and Yr ranging from 0.8 to 0.83, 0.9 to 1.0 and 0.75 to 1.0 respectively. For two-layer bed,it is found that the combination of n 1 = nvid = 2.99mm 2 = n,, = 5 can fit a the value

Heat Transfer of Alumina Sands in Fluidized Bed Combustor with Novel Circular Edge Segments Air Distributor

Fluidized bed combustor, which consists of a reaction chamber, an air distribution plate, uses inert particles, as its bed material. In order to ensure stable operation, it is apparent that the operating velocity of the air should be sufficiently large so that the flow rate through it is relatively undisturbed by the bed pressure fluctuation above it. However, high distributor pressure drop in fluidized bed system is undesirable because it will lead to high energy input in the blower to supply the fluidization air to fluidize the inert sand particles. Thus, the new novel designs of air distributor that consists of circular edge segments that contributed to low pressure drop and improvement of heat and mass transfer in fluidized bed combustor is introduced and will become primary interest of this research. The effects of temperature variations between an electrically heated tube immersed vertically in fluidized bed and alumina particles of various sizes were experimentally studied. In this paper, the data for heat transfer coefficient for an electrically heated vertical tube immersed vertically in fluidized bed combustor consists of alumina particles diameter ranging from (Full-size image (10 K)= 100, 177 and 250 μm) is reported at temperature from 50 oC to 250 oC

Improvement On Particulate Mixing Through Inclined Slotted Swirling Distributor In A Fluidized Bed: An Experimental Study

Previous studies show that excellent particulate mixing in a fluidized bed can reduce the operating cost during fluidization. Therefore, this paper investigates enhancement of particulate mixing in a fluidized bed by using novel inclined slotted swirling distributor. To reduce the cost of pumping power, small size, low pressure blower is used in the study. Moreover, Geldart group B bed materials with different bed aspect ratios and distributor designs viz., perforated plate, circular edged slots (90°) and novel swirling (45°) distributors are used. The novel distributor with 45° inclined slots was found to be effective at enhancing the circulation rate. Swirling flow pattern of the bed materials in a clock-wise direction is obvious in shallow bed, and two-layer transversal-lateral circulation motions are observed in deep bed. It can be concluded from the study that excellent particulate mixing as per rotated distributors is made possible by novel swirling-type distributor without the implementation of electric motor and mechanical rotation