Efficiency of a collector

The collector efficiency curve is a good indication for the performance of a collector at different operating temperatures. Optical and thermal losses influence the efficiency of a collector. Thermal losses depend on the temperature at which the solar thermal collector is operating. Simple constructed collectors like an unglazed swimming pool collector have high losses already at relatively low temperatures. Process heat collectors have special... 

In Ref. [41], it has been shown that the trapping efficiency can be increased by applying photonic crystals. A photonic structure that serves as a band-stop reflection filter for the light emitted from the dye increases the trapping efficiency of a collector preventing the escape from the system (as shown below). 

Gravimetric efficiency The efficiency of a dust collector to remove a given weight of particulate matter related to the total weight present in the air stream. 

Theoretical dependence of filter efficiency of a single collector (proportional to the rate at which particle contacts occur between particles and the filter grain by mass transport) on particle diameter. For particles of small diameters transport by diffusion increases with decreasing size. Contact opportunities of the larger particles with the filter grain are due to interception and sedimentation they increase with increasing size. 

When insufficient data are available, it may be necessary to generate test atmospheres to determine the physical state of a compound and the collection efficiency of a filter and vapor collector. The estimation of the vapor/particulate ratio may also depend on concentration and sample loading. For example, in a short sampling time, vapor may be efficiently collected on a filter, but longer term sampling may reveal saturation of the filter with vapor and eventual passage of the vapor into a backup bubbler or sorbent tube. 

The collection efficiency of a filter sampler was demonstrated by sampling test atmospheres with a backup collector at the proposed sampling rate and time, and analyzing the collected samples. For sorbents or filter/sorbent sampling trains, the breakthrough volume was determined (to demonstrate capacity) at 80% relative humidity. 6... 

In the collectors used, R is generally in the C2 to C6 range. Xanthates are readily oxidized to dixanthogens, and the extent of this reaction may have a big effect on the efficiency of the collector. 

The capacity of a collector is expressed in terms of its peak power production (Wp). This is the amount of electric power that a PV module is able to generate when it receives 1,000 watts per square meter of vertical solar irradiation at 25°C cell temperature. This is also called one sun. If this level of insolation existed for 24 h every day of the year, each m2 of collector area would receive 8,760 kWh/yr. The actual rate of power generation is naturally less. The value of Wp/ m2 of a module is also called its power density or efficiency. Therefore a 10% efficient module when receiving one sun will generate 0.1 kWp/m2 and a 15% will generate 0.15 kWp/m2. 

The effectiveness of deep-bed filters in removing suspended particles is measured by die value of die filter coefficient which in turn is related to the capture efficiency of a single characteristic grain of the bed. Capture efficiencies are evaluated in the present paper for nil cases of practical importance in which London forces and convective-diffusion serve to transport particles to the surface of a spherical collector immersed in a creeping How field. Gravitational forces are considered in some cases, but the general results apply mainly to submicron or neutrally buoyant particles suspended in a viscous fluid such as water. Results obtained by linearly superimposing the in-... 

Our approach to the problem of predicting the performance of fluidized bed filters involves logically coupling models that describe the flow behavior of the fluidized state with models that describe the mechanisms of particle collection. The collection mechanisms analysis leads to expressions for determining the collection efficiency of a single filter element. An example of a collection mechanism is inertial impaction by which a particle deviates from the gas stream lines, due to its mass, and strikes a collector. It should be noted that because particle collection mechanisms are functions of the fluid flow behavior in the vicinity of a collector, there exists an interdependency between fluidization mechanics and particle collection mechanisms. 

Many process systems require more than one piece of equipment to accomplish a given task, e.g., removal of a gaseous or particulate pollutant from a flow stream. The efficiency of each individual collector or equipment may be calculated using the procedure set forth in Problem CMA.2. The overall efficiency of multiple collectors may be calculated from the inlet stream to the first unit and the outlet stream from the last unit. It may also be calculated by proceeding sequentially through the series of collectors. 

Figure 17. Collection efficiency of model collector (i.e., a scaled-down version of the Caltech rotating arm collector) vs. generalized Stokes number. Predicted (----------) Experimental (H-— ).

Development of collector electrode materials with lower work function ( 1.0 eV) is the most effective methods to improve energy conversion efficiency of a thermionic converter. At present refractory metals such as Mo, W, Nb with cesium adsorption are used as a collector with the work function values of about 1.7eV. It is suggested that metal oxide collectors can adsorb cesium more strongly and show lower values of work function. In the study, refractory metal oxides and AgO x were experimentally examined concerning the work function values and high temperature durability. A research thermionic converter of a W emitter and an AgO x collector was fabricated and power generation tested to examine the effectiveness of the AgO x collector. A new type of a FGM collector which integrates a... 

The main reasons for the low efficiencies are the incomplete absorption of the solar spectrum by any single material which serves as a colorant. Self-absorption of the fluorescence by the emitting colorant. Critical cone losses of the reemitted centers, absorption and scattering of the host materials, lack of good contact between the LSC and the photovoltaic cell. Reflection of light from the metallic surfaces of which the electrical contacts are made. The decrease of performance efficiency of the collectors made of organic dyes with time are a result of photodecomposition of the colorant and polymeric host material. 

The modification is seen to parallel the incorporation of the Stokes-Oseen function (Eq. 8.3.24b) into the solution for the collector efficiency of a single cylindrical collector. A similar change would be made for an assemblage of cylindrical collectors, though the volume fraction function that would replace the Stokes-Oseen function would differ from the one for spherical collectors. 

Instantaneous Efficiency (of a Solar Collector) - The amount of energy absorbed (or converted) by a solar collector (or photovoltaic cell or module) over a 15 minute period. 

For a definite period, the so-called long-term efficiency of the collector can be expressed with the time integral of utilized and input energy flow rates... 

FIGURE 14.27 Instantaneous efficiency of a liquid-type collector as a function of inlet temperature parameter is the ambient temperature (a) single covering (b) double covering. (From Imre, L. and Kiss, L.I., in Numerical Methods in Heat Transfer, Vol. 2, R.W. Lewis, K. Morgan, and B.A. Schrefler, Eds., Wiley, Chichester, England, 1983, Chapter 15.)... 

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