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thermal collector
l The hot water is stored in an insulated storage tank where heat losses are minimal
l The hot water is passed to the adsorption chiller bed 1 where adsorption occurs by heating. At adsorption bed 2,
cooling water is used for the desorption process
l The water is then cycled to the hot bed where is reheated by the sun
l The adsorption system receives water from demand to cause further cooling
l The chilled water from the adsorption system is conveyed to the demand to cause cooling
Figure 1. Components of the proposed adsorption cooling system
The model was then programmed to estimate the average solar irradiance, followed by the average heat available at the collector. Next, the heat transferred to the water storage tank was determined using the approach proposed by Mahsa & Behbahani-nia, (2013), as per the equation 1 below:
Where is the mass flow rate of water through the storage tank; is the volumetric flow rate, is the density, is the specific heat capacity of water = 4.18kj /kgK, is the temperature difference between the circulating water and the collector temperature.
The average cooling loads of the building was then determined in the model with focus being on a 3-bedroom residential building after which the rate of heating was computed assuming an average Coefficient of Performance
(C.O.P) of 0.3. Finally, the performance of the system was evaluated based on its practicability, economics, affordability, durability and feasibility in Nairobi region.
Results
Based on the inputs to the model, automatic calculations were done by the model and the following outputs are discussed: 1) the estimation of the solar irradiance received during the study time; 2) determination of the energy used by the adsorption system, and 3) the number of collectors used to provide the required cooling load.
Average solar irradiance values
First, the average solar radiation per square meter of the FPC was determined. Notably, the amount of radiation received from the sun on a tilted surface is dependent on the location, the slope of the collector, and the efficiency
Engineering in Kenya Magazine Issue 002
47