Evaluation of Overall Heat Transfer Coefficient of Different Greenhouse Thermal Screens Using Building Energy Simulation

라쉬드아드난,이종원,이현우 (사) 한국생물환경조절학회 2018 생물환경조절학회지 Vol.27 No.4

In winter, thermal screens are widely used to reduce heat loss from greenhouse to save energy. Unfortunately, not much data are available to the farmer to compare thermal screens while selecting the one that meets their specific requirements. Thus, there is a need to investigate the thermal performance of thermal screens. To address this issue, the Building Energy Simulation (BES) model of a hot box was used to calculate the overall heat transfer coefficient (U-value) of the thermal screens. To validate the model, computed and experimental U-values of singleand double-layered polyethylene (PE) material were compared. This validated model was used to predict the U-values of the selected thermal screens under defined weather conditions. We quantified the U-values of each selected material and significant changes in their U-values were noted in response to different weather conditions. Notably, the thermal properties of the tested screens were taken from the previous literature to calculate U-values using the BES model. The U-values of the thermal screens can help researchers and farmers evaluate their screens and make pre-design decisions that suit their investment capabilities.

Efficiency of Different Roof Vent Designs on Natural Ventilation of Single-Span Plastic Greenhouse

라쉬드아드난,이종원,김현태,이현우 (사) 한국생물환경조절학회 2019 생물환경조절학회지 Vol.28 No.3

In the summer season, natural ventilation is commonly used to reduce the inside air temperature of greenhouse when it rises above the optimal level. The greenhouse shape, vent design, and position play a critical role in the effectiveness of natural ventilation. In this study, computational fluid dynamics (CFD) was employed to investigate the effect of different roof vent designs along with side vents on the buoyancy-driven natural ventilation. The boussinesq hypothesis was used to simulate the buoyancy effect to the whole computational domain. RNG K-epsilon turbulence model was utilized, and a discrete originates (DO) radiation model was used with solar ray tracing to simulate the effect of solar radiation. The CFD model was validated using the experimentally obtained greenhouse internal temperature, and the experimental and computed results agreed well. Furthermore, this model was adopted to compare the internal greenhouse air temperature and ventilation rate for seven different roof vent designs. The results revealed that the inside-to-outside air temperature differences of the greenhouse varied from 3.2 to 9.6oC depending on the different studied roof vent types. Moreover, the ventilation rate was within the range from 0.33 to 0.49 min-1. Our findings show that the conical type roof ventilation has minimum inside-to-outside air temperature difference of 3.2oC and a maximum ventilation rate of 0.49 min-1.

온실 관개를 위한 풍력에너지 이용 : 아시아 각국의 비교 연구

라쉬드아드난 ( Rasheed,A. ),이종원 ( Lee,J. W. ),이현우 ( Lee,H. W. ) 한국농공학회 2015 한국농공학회 학술대회초록집 Vol.2015 No.-

A simple methodology was used to evaluate the wind energy as an alternative energy source for the irrigation of greenhouse crops. The selected locations are Shouguang in China, Sargodha in Pakistan, and Buan and Gimhae in South Korea. The wind resources available at each site were evaluated to determine their potential for providing adequate and cost-effective supply of water to meet our greenhouse crop annual water requirement. Tomato crop was selected for this research work. The concept of LCOE was used for the economic assessment of all energy sources to check their adoption feasibility. While conducting this research various other factors were considered, such as wind resources available on each site, cost of technology, greenhouse size, crop water requirement, capacity of water storage tank, price of tomato, planting dates and duration of tomato crop and elevation of water to be pumped. Although LCOE associated with diesel pumping and electricity from the grid was low but these technologies required a continuous running and maintenance cost, in contrast wind pumping system required substantial initial capital relay, but maintenance and operational costs were almost negligible. Therefore, after payback period renewable energy sources can be utilized without running cost but just a little amount in the sense of maintenance cost. Shouguang (China) and Buan (South Korea) have adequate wind resources, it could be feasible to use wind-driven pumps for irrigation of greenhouse crops. The Average wind resources in Sargodha (Pakistan) and Gimhae (South Korea) are inadequate for the large area water pumping with wind pumps but medium size greenhouse could be achievable and also could be economically feasible.

온실 관개를 위한 풍력에너지 이용에 대한 타당성 평가

라쉬드아드난 ( Rasheed A ),이현우 ( H W Lee ),이종원 ( J W Lee ) 한국농업기계학회 2015 한국농업기계학회 학술발표논문집 Vol.20 No.1

BES를 이용한 핫박스 모델 개발 및 검증

라쉬드아드난 ( Adnan Rasheed ),이종원 ( Jong Won Lee ),이현우 ( Hyun Woo Lee ) 한국농공학회 2016 한국농공학회 학술대회초록집 Vol.2016 No.-

Building energy simulation (BES) model of hot box was developed by using TRNSYS, to investigate the overall heat transfer coefficient, U-vlaue(W · m^-1· k^-1) of different greenhouse covering materials based on specified weather conditions. The tests were carried out with extensively using greenhouse covering materials, polyethylene (PE), polycarbonate (PC), Polyvinyl chloride (PVC), and horticulture glass (HR). In addition we defined all test materials in TRNSYS on the bases of their optical and thermal properties. The model was calibrated by using different inside and outside convective heat transfer coefficient values suggested by different studies to find out the best relation with the experimental. The BES model of hot box shows very good agreement, when validated with experimentally obtained results. Furthermore, influence of different weather parameters, in which inside/outside temperature difference, wind speed, and long wave radiation losses are more drastic were investigated. It was found that U-value increases with increase in temperature difference. And for the given temperature difference U-value increase as wind velocity increases. The effect of night sky radiation were found higher for the low temperature difference and significant change occurs when temperature difference reaches 20 ℃.

Evaluation of Overall Heat Transfer Coefficient of Different Greenhouse Thermal Screens Using Building Energy Simulation

Adnan Rasheed(라쉬드아드난),Jong Won Lee(이종원),Hyun Woo Lee(이현우) (사)한국생물환경조절학회 2018 생물환경조절학회지 Vol.27 No.4

겨울철에 열손실을 줄이기 위해 많은 온실에서 보온커튼을 사용하고 있다. 그러나 적절한 보온커튼을 선택할 때 판단 자료로 활용할 수 있는 명확한 기준이 없는 실정이며 이를 위해서는 보온재의 보온 특성에 대한 정량적인 값이 필요하다. 본 연구에서는 BES를 사용하여 보온커튼의 관류열전달계수를 산정하는 시뮬레이션 모델을 개발하였다. 일중 및 이중 PE필름 피복에 대한 관류열전달계수의 실험값을 사용하여 시뮬레이션 결과를 검증하였다. 검증된 모델을 사용하여 문헌에서 제시된 각종 열적 특성을 가진 보온커튼에 대한 관류열전달계수를 산정하고 비교분석하였다. 개발된 시뮬레이션 모델은 다양한 보온커튼의 관류열전달계수를 산정하는데 활용될 수 있을 것이며, 제시된 관류열전달계수는 보온커튼의 성능을 정량적으로 비교하는데 유용하게 활용될 수 있을 것으로 판단된다. In winter, thermal screens are widely used to reduce heat loss from greenhouse to save energy. Unfortunately, not much data are available to the farmer to compare thermal screens while selecting the one that meets their specific requirements. Thus, there is a need to investigate the thermal performance of thermal screens. To address this issue, the Building Energy Simulation (BES) model of a hot box was used to calculate the overall heat transfer coefficient (U-value) of the thermal screens. To validate the model, computed and experimental U-values of singleand double-layered polyethylene (PE) material were compared. This validated model was used to predict the U-values of the selected thermal screens under defined weather conditions. We quantified the U-values of each selected material and significant changes in their U-values were noted in response to different weather conditions. Notably, the thermal properties of the tested screens were taken from the previous literature to calculate U-values using the BES model. The U-values of the thermal screens can help researchers and farmers evaluate their screens and make pre-design decisions that suit their investment capabilities.

Comparison of Environmental Conditions and Insulation Effect between Air Inflated and Conventional Double Layer Greenhouse

메쓰캄카남즈사니카닐란가니자야세카라,나욱호,오우라비압둘하메드바바툰데,이종원,라쉬드아드난,김현태,이현우,Jayasekara, Shanika N.,Na, Wook H.,Owolabi, Abdulhameed B.,Lee, Jong W.,Rasheed, Adnan,Kim, Hyeon T.,Lee, Hyun W. The Korean Society for Bio-Environment Control 2018 생물환경조절학회지 Vol.27 No.1

본 연구는 공기주입 이중피복온실과 관행 이중피복온실의 생육환경과 단열성능을 비교하기 위하여 수행하였다. 두 온실의 온도, 상대습도, 포차, 이산화탄소농도, 일사량, 딸기 생산량 및 난방연료소비량을 비교하였다. 공기주입온실이 관행온실보다 야간에 상대습도가 더 높고 포차는 더 낮게 나타나 딸기의 생육에 좋지 않은 환경을 보여주었다. 이산화탄소농도는 공기주입온실이 관행온실보다 더 높게 나타났으며, 이는 공기주입온실이 더 밀폐되어 있어 환기량이 적기 때문인 것으로 판단된다. 관행온실의 광투과율이 77%로 공기주입온실의 72%보다 더 높아 관행온실의 광환경이 더 우수한 것으로 나타났다. 관행온실의 딸기 생산량이 더 높게 나타났으며, 이는 관행온실의 생육환경이 공기주입온실보다 더 우수한 결과로 판단된다. 난방연료는 공기주입온실에서 더 적게 소모되어 공기주입온실의 단열성능이 더 우수한 것으로 나타났다. This study was conducted to determine which greenhouse provided good environmental conditions for strawberry production, and performed better at conserving energy. Temperature, RH, VPD, $CO_2$, solar radiation, yield, and fuel consumption were the parameters analyzed. The temperatures of both greenhouses were well controlled in order to provide optimal day and night temperatures for strawberry production. The air inflated double layer greenhouse had higher RH values (more than 90% at night), which led to higher disease occurrence, in comparison to the conventional double layer greenhouse. Furthermore, the air inflated double layer greenhouse had lower VPD values than the conventional double layer greenhouse. Therefore, better RH and VPD were observed in the conventional double layer greenhouse. Higher $CO_2$ concentration was observed in the air inflated double layer greenhouse while the conventional double layer greenhouse ventilated better than the air inflated greenhouse, because of its side ventilators. Moreover, higher solar radiation in the conventional double layer greenhouse resulted in higher yield, in comparison to the air inflated double layer greenhouse. Thus, we can conclude that the conventional double layer greenhouse provided a better environment for crop growth, in comparison to the air inflated double layer greenhouse. Regarding fuel consumption, the air inflated double layer greenhouse had lower fuel consumption than the conventional double layer greenhouse. Therefore, from an energy consumption point of view, we can conclude that the air inflated double layer greenhouse performed better than the conventional double layer greenhouse.

온실 유형별 설비 및 작물하중 분석

이현우 ( Hyun Woo Lee ),라쉬드아드난 ( Adnan Rasheed ),이종원 ( Jong Won Lee ),나욱호 ( Wook Ho Na ),곽철순 ( Cheul Soon Kwak ) 한국농공학회 2016 한국농공학회 학술대회초록집 Vol.2016 No.-

한국의 온실구조 설계기준 및 해설, 일본의 원예용시설안전구조기준(잠정기준), 유럽의 EN1991-1-3, 미국의 온실구조설계 매뉴얼에서 제시하고 있는 설비하중과 작물하중 기준을 서로 비교하였다. 또한 우리나라에서 사용하고 있는 온실에 대해 유형별로 온실구조와 설비 및 작물하중의 특성을 비교하였다. 한국기준의 설비하중은 유럽의 기준과 유사하게 차광시스템과 관수장비에 대하여 설계하중을 제시하고 있으나 구체적인 값은 다르게 제시하고 있어 이에 대한 검토가 필요할 것으로 판단된다. 일본의 설비하중 기준에서는 가장 불리한 조건과 동적영향을 고려하도록 규정하고 있다. 미국의 설비하중기준에서는 작물하중을 포함한 최대 설비하중을 제시하고 있다. 한국기준의 작물하중은 유럽의 기준과 동일한 값을 제시하고 있으며 토마토, 오이, 딸기, 분화에 대해서만 구체적인 값을 제시하고 있다. 일본의 기준에서는 모든 작물에 대하여 동일한 값을 제시하고 있으나 최근 재배시스템의 많은 변화가 있기 때문에 이러한 변화를 고려한 작물하중에 대한 규명이 필요할 것으로 판단된다.

Determination of Thermal Radiation Emissivity and Absorptivity of Thermal Screens for Greenhouse

rafiq adeel,나욱호,라쉬드아드난,김현태,이현우 (사) 한국생물환경조절학회 2019 생물환경조절학회지 Vol.28 No.4

Greenhouse farmers often use thermal screens to reduce greenhouse heating expenses during the winter, and for shade during hot, sunny days in the summer, as it is an inexpensive solution to temperature control relative to other available options. However, accurate measurements of their emitted and absorbed radiations are important for the selection of suitable screens that offer maximum performance. Material’s ability to save energy is highly dependent on these properties. Limited studies have investigated the measurement of these properties under natural conditions, but they are only applicable to materials having partial porosities. In this work, we describe a new radiation balance method for determining emissive power and absorptive capacity, as well as reflectivity, transmissivity and emissivity of materials having complete and partial transparency by using pyrgeometer and net radiometer. In this study, four materials with zero porosity, were tested. The emissivity value of PE, LD-13, LD-15 and PH-20 was 0.439±0.020, 0.460±0.010, 0.454±0.004, and 0.499±0.006, respectively. All tested samples showed high emitted radiation as compared to absorbed radiation.

온실의 구조설계용 작물하중 산정

나욱호(Wook-Ho Na),이종원(Jong-Won Lee),라쉬드아드난(Adnan Rasheed),곽철순(Cheul-Soon Kwak),이시영(Si-Young Lee),윤용철(Yong-Cheol Yoon),이현우(Hyun-Woo Lee) (사)한국생물환경조절학회 2017 시설원예‧식물공장 Vol.26 No.4

본 연구에서는 온실의 구조설계용 작물하중을 산정하는데 필요한 기초자료를 제공하기 위하여 각국의 온실구조설계용 작물하중 기준들을 비교분석하고 여러 가지 온실작물들에 대하여 작물하중을 직접 측정하고 분석하였다. 설계 작물하중에 대한 각국의 기준들을 비교분석한 결과 나라들 마다 서로 많은 차이를 보여주고 있으며, 우리나라 기준들은 외국의 기준들을 그대로 인용하고 있는 것으로 나타나 우리나라 실정에 맞는 작물하중 기준이 제시될 필요가 있다고 판단된다. 최대 주당 작물하중이 토마토는 두 가지 온실에서 각각 3.3kgf·plant<SUP>-1</SUP>와 3.9kgf·plant<SUP>-1</SUP>로 나타났고, 오이는 0.75kgf·plant<SUP>-1</SUP>, 가지는 1.9kgf·plant<SUP>-1</SUP>, 딸기는 재배베드를 포함하여 2.1kgf·plant<SUP>-1</SUP> 으로 나타났다. 단위면적당 작물하중은 토마토가 평균 8.5kgf·m<SUP>-2</SUP>으로 나타났고, 오이와 가지는 각각 2.1kgf·m<SUP>-2</SUP>과 2.4kgf·m<SUP>-2</SUP>으로 토마토의 하중보다 훨씬 낮게 나타났다. 우리나라 온실설계기준에 제시된 작물하중은 토마토와 오이의 경우 15kgf·m-2으로 본 연구에서 측정된 값보다 훨씬 높았다. 우리나라의 설계기준이 네덜란드의 기준을 그대로 인용한 것으로 판단되기 때문에 이러한 차이를 고려하여 우리나라의 작물하중 설계기준에 대한 재검토가 이루어져야 할 것으로 판단된다. 딸기의 작물하중은 행잉베드를 포함한 중량이 21.0kgf·m<SUP>-2</SUP>로 네덜란드의 설계기준인 30kgf·m<SUP>-2</SUP>보다 훨씬 작았다. This study was conducted to provide basic data needed to calculate the crop loads for the greenhouse design. Four countries’ crop loads for greenhouse structures were compared and the crop loads were measured directly and analyzed for various greenhouse crops, including tomato, strawberry, cucumber, and eggplant. According to the analysis results of four country’s standards for the design crop loads, it was judged that the new design crop loads suit for greenhouse crops in our country should be suggested because our standards just used the design crop loads of other countries. The maximum crop loads per plant of tomato, cucumber, eggplant, and strawberry were 3.9, 0.75, 1.9 and 2.1 kgf·plant<SUP>-1</SUP>, respectively. The crop load per unit area of tomato was 8.5 kgf·m<SUP>-2</SUP>, which was much greater than the cucumber and eggplant’s crop load of 2.1 and 2.4 kgf·m<SUP>-2</SUP> respectively. The crop loads of tomato and cucumber, suggested by the greenhouse structure design standard of Korea, is 15 kgf·m<SUP>-2</SUP>, which is far greater than the values suggested by this research. It was judged that this was because our standard just used the Dutch standard, our crop load standard should be reviewed considering this difference. The crop load of strawberry, including the growing bed, was 21.0 kgf·m<SUP>-2</SUP>, which was much greater than the crop load in the Dutch standard.