A review of common natural ventilation and evaporative cooling systems for Greenhouses and the Nigerian reality

Greenhouses simulate the "desired" environment for successful growth and development of plants. They, by design, achieve this desired environment by supplying the necessary climatic inputs needed by the plants to strive and at the same time exclude factors impeding the growth of plants, hence it is called a controlled environment. One of the common and most desired attribute of the greenhouse is its ability to provide effective cooling to the plants. This paper reviewed, extensively, the concept of evaporative cooling as applied in greenhouses. Factors like Vapor Pressure deficit (VPD), Relative Humidity, Ambient Temperature were also discussed with regards to its effects on the efficiency of the evaporative cooling system. The efficiencies of the Fan and Pad System and the Fog systems were reviewed and compared with their consequent dependence on factors like nozzle spacing, nozzle length, saturation efficiency of pad material etc. The Natural Ventilation method was also reviewed as a "stand alone " greenhouse cooling method and as an augmentation to other cooling systems. Factors like rate of air exchange, total area of vents, wind speed, vent opening angles etc. were also discussed in line with their effects on the effectiveness of the Natural ventilation method. The Nigerian Perspective on Greenhouses and its Cooling methods was also discussed with reference to local development of evaporative coolers as well as its importation, its affordability, management, availability and appliance to the Nigerian farming culture.

Effect of pad water flow rate on evaporative cooling system efficiency in laying hen housing

An experiment was conducted in three commercial laying hen houses with 32-week-old hens in the summer of 2017 in a commercial farm in Gharbia Province, Egypt (31.06ºN, 31.16ºE) using an evaporative pad cooling system to determine the most suitable water flow rate for maintaining indoor air temperature within the thermal comfort zone. The experiment was conducted using three different water flow rates, i.e. 4.76, 5.65, and 6.35 L min–1.m–2, to assess the effect of different water flow rates on evaporative pad cooling system performance and determine the most suitable water flow rate for maintaining the thermal comfort zone of laying hens. The evaporative pad cooling system maintained the mean indoor air temperature below 28°C. The mean indoor air relative humidity during the experimental period ranged from 72.6 to 73.8%. The 4.76 L min–1.m–2 water flow rate resulted in the highest saturation efficiency (ca. 73.75%). In contrast, the 6.35 L min–1 m–2 water flow rate resulted in the lowest saturation efficiency (70.63%). The mean cooling energy values were 69.11, 66.0, and 66.65 kwh for water flow rates of 4.76, 5.56, and 6.35 Lmin–1m–2, respectively. The highest temperature-humidity index was 27.78°C, which indicated that birds were not stressed in all treatments.

Experimental Investigation of the Potential of a New Fabric-Based Evaporative Cooling Pad

Direct evaporative coolers are energy-efficient, economic solutions to supplying cooling demand for space conditioning. Since their potential strongly depends on air hygrothermal conditions, they are traditionally used in dry and hot climates, though they can be used in many applications and climates. This work proposes a new direct evaporative cooling system with a fabric-based pad. Its design enables maximum wetted surface with minimum pressure drop. Its performance has been experimentally characterized in terms of saturation efficiency, air humidification, pressure drop, and level of particles, based on a full factorial Design of Experiments. Factors studied are air dry bulb temperature, specific humidity, and airflow. Saturation efficiencies obtained for a 25 cm pad are above the values achieved by other alternative evaporative cooling (EC) pads proposed in the literature, with lower pressure drops.

Refrigeration Capacity and Effect of Ageing on the Operation of Cellulose Evaporative Cooling Pads, by Wind Tunnel Analysis

This study investigates the temperature reduction capacity and water consumption of a fan-pad system installed in a greenhouse located in the coastal regions of Almería. The suitability of this system for coastal zones with high environmental humidity during the summer is analyzed. Historical temperature and relative humidity series are studied, obtaining the thermal difference and maximum, medium, and minimum monthly water consumption of the pads based on the operation data of the pads. Despite the high relative humidity of the air in the hottest hours of the day, a decrease of 5.92 °C in the mean temperature and a water consumption of 13.55 l/h per square meter of an evaporative cooling pad are obtained in the month of August. Additionally, the operation of a cellulose evaporative cooling pad installed for 3 years in a greenhouse is analyzed in a wind tunnel and compared with that of a new pad of the same model. Over time and with low maintenance, the porosity of the pad decreases due to salt incrustation. The salt incrustation makes airflow more difficult in the pad, increasing the pressure drop by 170.04%; however, the air saturation efficiency of the pad increases by 6.6% due to the greater contact time between the air and the water.

Experimental Evaluation of Evaporative Cooler Using Agro Materials

The purpose of the study is to investigate the direct evaporate cooler in hot and humid regions with two different types of agro-based materials. In our experimental study, the locally available agro materials luffa (Sponge Gourd), zizanioides (Vetiver) were used with various thickness and the experimental results were compared with mathematical values. The operating parameters of pad thickness, air velocity, were changed and the performance of the cooler was analyzed. A test rig was designed and fabricated to collect experimental data. The performance of the evaporative cooler was evaluated based on the ambient condition. The analysis of the data indicated that cooling saturation efficiency improve with decrease of air velocity and higher pad thickness. It was shown that zizanioides-based pad with 160[Formula: see text]mm thickness has the higher performance (88%) at 4.5[Formula: see text]m/s air velocity in comparison with luffa pad materials. The experimental results of outlet air temperature and number of transfer units (NTU) were compared with mathematical model. The test results were within the limit of 15% and 10% to mathematical values.

EXPERIMENTAL STUDY OF A CYCLONE SCRUBBER AIR CONDITIONING SYSTEM USING FACTORIAL DESIGN

This work reports the results obtained in the experimental evaluation of an American type cyclone which has been modified and adapted to perform environmental air conditioning by evaporative cooling. Equipment was fitted with nozzles atomizers, which perform the injection of liquid transversely to the gas stream. The tests were carried out following a full factorial design of experiments in order to obtain the influence of the atomizer holes diameter and of the liquid/air flow ratio on the cyclone performance. The diameter of the atomizer insert holes was in the range of 2.8 to 3.6 mm and the liquid/air flow ratio was from 0.65 to 0.76 L/m3. The saturation efficiency (Es) of the cyclone was analyzed through the Response Surface Methodology (RSM). Saturation efficiencies between 45.9 and 62.2 % were obtained. The use of statistical techniques allowed the proposition of empirical correlations to predict the behavior of the system regarding the studied operational range. The results show that the cyclone scrubber equipment is a viable alternative to air conditioning for human standards.

PENGURANGAN KADAR H2S DARI BIOGAS LIMBAH CAIR RUMAH SAKIT DENGAN METODE ADSORPSI

Biogas sebelum digunakan harus dimurnikan terlebih dahulu dari kandungan asam sulfida (H2S) yang meskipun jumlahnya kecil namun menimbulkan kerugian karena menimbulkan korosi pada logam atau apabila dibakar akan membentuk SO2 atau SO3 yang dikenal dengan SOx yang menyebabkan terjadinya hujan asam. Tujuan dari penelitian ini adalah mencari waktu jenuh adsorben dalam menjerap H2S, mengetahui kemampuan adsorben karbon aktif dalam menyerap dan mencari konstanta persamaan adsorpsi isotherm Freundlich pada variasi ukuran karbon aktif yang digunakan dalam menghitung waktu tinggal adsorpsi. Bahan yang digunakan adalah sludge dari hasil pengolahan limbah cair rumah sakit. Metode yang dilakukan dalam penelitian ini yaitu mengukur kandungan H2S dalam biogas sebelum melalui adsorber disusun secara seri ukuran tinggi kolom 70 cm, diameter ½ inch, tinggi isian 64 cm bahan isian karbon aktif dengan ukuran 4, 7, 10, 12, 14 mesh kecepatan biogas 0.5 liter/menit diperoleh hasil karbon aktif paling cepat mengalami kejenuhan ukuran 4 mesh yaitu 60 menit, H2S yang terjerap 202.42 unit dari effisiensi kejenuhan 9.76% sedangkan waktu jenuh paling lama 90 menit ukuran karbon aktif 14 mesh H2S yang terjerap 368.65 unit effisiensi kejenuhan 9.79%. Karbon aktif yang optimal digunakan yaitu 12 mesh waktu jenuh 80 menit, effisiensi kejenuhan 9.82% dengan waktu tinggal 127.927 detik sedangkan waktu tinggal paling singkat terjadi pada ukuran adsorben 4 mesh, yaitu waktu tinggal 73.855 detik. Keywords: limbah, biogas, adsorpsi, asam sulfida, karbon aktif Biogas is purified before being used in from the acid content of sulfide (H2S), although the numbers are small, but the resulting loss due to corrode metal or when burned to form SO2 or SO3, known as SOx that cause acid rain. The purpose of this study to find time in the saturated adsorbent adsorb H2S, the ability of the activated carbon adsorbent adsorb adsorption equation and find the constants in the Freundlich isotherm variations in the size of activated carbon for in calculating the residence time of adsorption. The materials used are the sludge from the hospital wastewater treatment. The method was performed in this study for measure the content of H2S in the biogas before passed through to the third adsorber column 70 cm height, ½ inch diameter, 64 cm high filling packing material of activated carbon with a size of 4, 7, 10, 12, 14 mesh velocity biogas 0 , 5 litre. / min obtained results most rapidly activated carbon burnout mesh size of 4 is 60 minutes, H2S is adsorption 202.42 mg of 9.76% while the efficiency of saturation saturation time exceeding 90 minutes 14 mesh size activated carbon is adsorption H2S 368.65 mg 9.79% saturation efficiency. Optimal use of activated carbon which is 12 mesh saturated 80-minute time, efficiency saturated 9.82% with a residence time of 127.927 seconds while the shortest residence time occurs on the mesh size of adsorbent 4, the residence time of 73.855 seconds. Keywords: waste , biogas, adsorption, acid sulfide, activated carbon