Performance Analysis of a Greenhouse Fan-Pad Cooling System: Gradients of Horizontal Temperature and Relative Humidity

Year 2015, Volume: 21 Issue: 1, 132 - 143, 24.12.2014

Mehmet Ali Dayıoğlu , Hasan Hüseyin Silleli

https://doi.org/10.15832/tbd.25721

Cited By: 5

Abstract

An experimental study was conducted to determine the performance parameters of system, as well as gradients of temperature and humidity along greenhouse when opening fan-ped cooling system. Measurements related with greenhouse environment were carried out by using seven sensors for different locations, as well as portable instruments. For this purpose, the five digital temperature and humidity sensors and two pyranometers were used during experiments. Among them, two were located outside greenhouse for external measurements. The rest one pyranometer above the crop canopy, four temperature and humidity sensors were mounted within the crop canopy along the greenhouse. Four sensors were placed according to positions defined between pad and fan. According to the experiment results, the non-uniform temperature changes, but approximately uniform humidity changes due to the crop transpiration were observed along greenhouse from pad panels to exhaust fans.

When the cooling system closed, hourly mean temperature and relative humidity from pad to fan inside greenhouse changed between 30–33°C and 30–47%, respectively, at outside climate conditions of 32°C and 25%. After providing stabile cooling by opening fan-pad system, hourly mean temperature and relative humidity along greenhouse from pad to fan ranged between 20 – 27°C, and 50 – 68%, respectively. The air temperature entering to greenhouse with air velocity of 0.8–0.9 ms^-1 through pad was approximately 12–13ºC lower than the outside air temperature. The air temperature from pad to fan increased approximately by 7 ºC.

The method of psychrometric calculations was employed to determine the cooling efficiency of fan-pad system. According to the calculation result, the average of air temperatures inside greenhouse was 24.5 ºC after achieving stable cooling for outside air temperature of 31.4 ºC. The hourly mean cooling effect and cooling efficiency calculated for fan-pad system were determined to be 6.96ºC and 76.8%, respectively.

Keywords

Greenhouse; Fan-pad cooling system; Temperature and relative humidity; Psychrometric calculation; Cooling efficiency

Sera Fan-Pad Soğutma Sisteminin Performans Analizi: Yatay Sıcaklık ve Bağıl Nem Değişimleri

Abstract

Fan-Pad soğutma sistemi çalışırken sera boyunca oluşan sıcaklık ve bağıl nem değişimleri ve soğutma sistemi performans parametrelerini saptamak için deneysel bir çalışma yapılmıştır. Çalışmada ölçümler yedi farklı noktaya yerleştirilen sensörler ve taşınabilir ölçüm cihazları kullanılarak gerçekleştirilmiştir. Bu amaçla, beş dijital sıcaklık-nem sensörü ve iki güneş ışınım sensörü kullanılmıştır. Sensörlerden ikisi sera dışına, bir güneş ışınım sensörü bitki örtüsü üstüne, dört sıcaklık-nem sensörü sera boyunca bitki örtüsü içine yerleştirilmiştir. Dört sensörün yerleşimi Pad ve Fan arasında tanımlanmış konumlara göre yapılmıştır. Elde edilen deney sonuçlarına göre, Pad tarafından fan tarafına sera boyunca homojen olmayan sıcaklık değişimleri, ancak transpirasyon nedeniyle yaklaşık homojen kalan bağıl nem değişimleri gözlemlenmiştir. Soğutma sistemi kapalı olduğu zaman, havanın 32 °C ve % 25 olduğu koşullarda, sera içinde Pad tarafından fan tarafına saatlik ortalama sıcaklık ve bağıl nem değerleri sırasıyla 30–33 °C ve % 30–% 47 arasında değişmiştir. Fan-Pad sistemi çalıştırılıp kararlı soğutma sağlandıktan sonra, sera boyunca saatlik ortalama sıcaklık ve bağıl nem değerleri sırasıyla 20 – 27 °C ve % 50 –% 68, arasında değişmiştir. Islak Pad yüzeyini geçerek yaklaşık 0.8–0.9 m s-1 hava hızla seraya giren hava sıcaklığı dış hava sıcaklığından 12–13 ºC daha düşük olmuştur. Pad tarafından fan tarafına sera boyunca hava sıcaklığı yaklaşık 7 ºC yükselmiştir. Buharlaşmalı Fan-Pad sisteminin soğutma etkinliğini hesaplamak için psikrometrik hesaplama yöntemi kullanılmıştır. Hesaplama sonucuna göre, dış hava sıcaklığının 31.4 ºC olduğu koşullarda kararlı soğutma sağlandıktan sonra sera içindeki ortalama sıcaklığın 24.5 ºC olduğu belirlenmiştir. Fan-Pad sistemi için hesaplanan saatlik ortalama soğutma etkisi ve soğutma etkinliği değerleri sırasıyla 6.96 ºC ve % 76.8 olarak saptanmıştır

Keywords

Soğutma etkinliği, Fan-Pad soğutma sistemi, Sera, Psikrometrik hesaplama, Sıcaklık ve bağıl nem

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