Category EuroSun2008-7

Experimental setup

Two different sets of experiments were carried out to prove the advancements on the distribution system.

Подпись: Fig. 3. Experimental setup to determine the optimum size and number of discharge points for the distributor (upper), and to check the LiCl diffusion through the textile (lower).

1. The objective of the first test is to determine the optimal size and number of discharge points distributed along the plastic tube. The optimized tube will serve the LD flow rate required by the application and ensure fairly equal amounts of the LD throttled-out through each discharge bore. Five perforated plastic tubes are tested. Each tube is perforated by a CNC machine in equally-spaced positions. H2O/LiCl (30% salt concentration by weight) is used as the liquid desiccant with three volume flow rate values. In order to investigate the effect of the distance between the LiCl feed-box and the discharge-point location, different positions along the tube are selected...

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Heating power and COP

As for the cooling operation, for the following statistics on hourly values, only hours with a constant operation of the machine were considered in order to be sure to consider steady state conditions only. This covers more than 63% of the hours with operation, as can be deduced from Table 1. Fig. 8 shows the frequency diagrams of the hourly COP and heating powers (Fig. 9). For the whole heating operation period a thermal COP of 1.43 is obtained. The hourly mean heating power was 9.43kW with a standard deviation of 1.59kW.


in the period between 11:30 and 14:30.

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Simulation Model and Validation

A detailed full dynamic simulation model of the installed system which considers the electricity consumption of all installed components (fans, pumps, etc.) has been developed by zafh. net in the simulation environment INSEL [5]. The simulation model is used to analyse the effect of different storage charge and discharge options. A very small time step of 10 seconds is used for an accurate consideration of all thermal capacities in the complex system. The complete model has been validated against measured data of the installed system. Figure 2 shows the measured performance of the solar cooling system together with the simulation results for one day in August 2007 [1]...

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Analysis of the results

The first set of experimental data for the distribution tube was analyzed by the factorial design analysis using MINITAB version 15.

Factorial design analysis is a statistical method in which every level of one factor is tested in combination with every level of another factor. In general, in a factorial analysis, all possible combinations of factor levels are tested [5].

Four variables (factors) were considered to have the highest influence on the distribution test. The first factor is the LiCl volume flow rate with three treatments (levels) with a range between 0.3 l/min-1.2 l/min. The second factor is the bore size with five levels, ranges between 0.5 mm – 0.9 mm...

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Operation temperatures

Fig. 10 shows the statistics of the driving temperatures. It can be seen, that in the heating mode driving temperatures below 68°C were also used. Unlike in the cooling mode, where the temperature in the buffer storage is used in order to decide whether high enough temperatures are available for operation, in the heating mode the machine is switched on whenever heating is required, assuming that the temperature in the heating net is always high enough. From the resulting operation conditions it can be seen that the available temperatures in the heating net present a high variation and are not constant at 72°C as the design values may suggest.

The temperatures fed into the heating coil (Fig. 11) were moderate (24°C to 30°C) and those from the boreholes where quite high (13-15°C). In Fig...

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Results of most promising cases

In table 1 the selected building applications and energy efficiency standards are described.

[7] Coefficient of Performance (COP) = cooling or heating output (kW) divided by

electrical input. The only electrical input is 4 small circulation pumps and internal controls. COP in conventional compressor-based chillers and packaged air conditioning units is usually stated as cooling capacity (kW) divided by compressor electrical input. Since the Millennium MSS air conditioning doesn’t have a refrigeration compressor, COP is stated here as annual cooling/heating energy delivered divided by total electrical input of the pumps and internal controls.

Fig 1. Millennium MSS Air Conditioning system heating and cooling device The example below shows one of the two barrels discharging cooling.

[8] chi...

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Heating and Cooling with a Small Scale Solar Driven Adsorption. Chiller Combined with a Borehole System

Dr. Tomas Nunez*; Bjorn Nienborg; York Tiedtke

Fraunhofer-Institut for Solar Energy Systems ISE, Heidenhofstrafte 2, 79106 Freiburg, Germany
* Corresponding Author, tomas. nunez@ise. fraunhofer. de


The performance of a solar driven adsorption cooling system is presented in this paper. The system consists of a reversible 5.5kW adsorption machine from the German company SorTech, a 20m2 flat plate collector field with a 2m3 buffer storage and a borehole array of three 80m boreholes. In the summer period, the adsorption machine is operated as a chiller driven by solar energy while the boreholes are used for heat rejection. In winter it is operated as a heat pump driven by the heat from a heating network and using the boreholes as low temperature heat source...

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G. Gutierrez*, P. Rodriguez, A. Lecuona, M. Venegas, J. Nogueira

Universidad Carlos III de Madrid (UC3M). Departamento de Ingenieria Termica y de Fluidos. Avda.
Universidad 30, 28911 Leganes, Madrid, Spain

* Corresponding Author, glgutier@ing. uc3m. es


An experimental facility applying the concept of adiabatic absorption has been designed and built in Universidad Carlos III de Madrid. Plate heat exchangers are incorporated in the design functioning as generator, condenser, sub-cooler and solution heat exchanger. Other components include a separator and two fin-coiled tubes as evaporators. Trials were carried out in order to characterize components and performance. The range of controlled hot fluid temperature corresponds to a solar thermal energy source (below 100°C)...

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