Myoung-Souk Yeo

Application of artificial neural network to predict the optimal start time for heating system in building

The artificial neural network (ANN) approach is a generic technique for mapping non-linear relationships between inputs and outputs without knowing the details of these relationships. This paper presents an application of the ANN in a building control system. The objective of this study is to develop an optimized ANN model to determine the optimal start time for a heating system in a building. For this, programs for predicting the room air temperature and the learning of the ANN model based on back propagation learning were developed, and learning data for various building conditions were collected through program simulation for predicting the room air temperature using systems of experimental design. Then, the optimized ANN model was presented through learning of the ANN, and its performance to determine the optimal start time was evaluated.

Energy Efficiency Analysis of Internally and Externally Insulated Apartment Buildings

Abstract Apartment buildings are the most common type of residential buildings in Korea, where hot water heating pipes are installed in the floor structures. An internal insulation system (IIS) has been applied to the outside walls of most Korean apartment buildings, so there are many cases in which the layer of insulation is disconnected by structural components at the wall-slab joints. These joints become thermal bridges where heat transfer increases. An external insulation and finish system (EIFS) is a possible solution to this problem. In this study, the surface temperature distributions of actual apartment buildings with an IIS and an EIFS were investigated with an infrared thermal imaging camera. Annual heat losses and gains through the wall-slab joints with an IIS and an EIFS were calculated by three-dimensional transient heat transfer simulations in which hot water heating was excluded and included, respectively, in order to evaluate not only the heating and cooling loads, but also the heating efficiency when the building is actually heated. The results show that the amount of heat transfer through the wall-slab joints with an IIS is considerable, even though additional insulation is installed under the slab, and the EIFS significantly reduces the heating and cooling loads and improves the heating efficiency.

Optimized control algorithm for automated Venetian blind system considering solar profile variation in buildings

Automated blinds need to be controlled to maximize benefits of daylight to enhance occupant comfort and to reduce energy consumption. However, previous control methods focused on minimizing the negative impacts of daylight, but failed to maximize the positive impacts of daylight and solar heat gain. The objective of this study is to develop an optimized control algorithm for automated venetian blind which would reduce the negative effects of incoming daylight on visual comfort of occupants, and to minimize psychological anxieties caused by frequent motions of the blind, by maximizing the positive effects of incoming daylight and solar irradiation, by opening/closing of the blind. Through implementation of the proposed methods and algorithms, the direct glare on work-planes could be prevented at all time, and also incoming daylight and solar irradiation could be increased.

Optimum Blind Control at the End of Operation Time Zone for Preventing Glare on Work-plane and Maximizing Daylight and Solar Heat Gain

The objective of this study is to develop the blind control strategy and method which reduce negative effect of incoming daylight on visual comfort of occupants, minimize psychological anxieties caused by frequent motions of a blind, and maximize positive effect of incoming daylight and solar irradiation by opening/closing of a blind. As previous researches on blind controls have limited outdoor environmental conditions to those in specific regions, orientations and dates, these resulted in problems at various conditions for general-purpose application. Major problem is that the time interval and amount of blind movement do not meet the control objective at the end of control zone and discontinuous curve. To overcome these limitations revealed in the previous researches, following tasks were performed in this study. 1) To establish the control objective to accomplish the goal of this study. 2) To develop the control methods and algorithms which prevent glare on the work-plane at any time and which control the time interval and amount of blind movement to follow the control objective at various profile angle curves. 3) To validate the general-purpose applicability and performance of the developed control methods and algorithms by simulation and its data analysis at various conditions. It was found that the proposed methods and algorithms can prevent the direct glare on the work-plane at all the time and also increase the incoming daylight and solar irradiation.

Design Parameters of Double-Skin Façade for Improving the Performance of Natural Ventilation in High-Rise Residential Buildings

In high-rise residential buildings, problems arise with the use of natural ventilation, as outdoor wind speed and pressure increase in accordance with the increase of building height. As an alternative for high-rise residential buildings, the double-skin façade offers a way to use natural ventilation. From a questionnaire conducted with residents of high-rise residential buildings and interviews with residential managers, problems relating to ventilation were identified and the improvement factors of natural ventilation were developed for the current plans of a double-skin façade. The evaluation parameters included the type of position for the inlet and outlet, the envelope module, external window, width of intermediate space, and internal windows. These parameters are derived from the method of architectural planning. The purpose of this study is to evaluate the natural ventilation performance in high-rise residential buildings, especially in terms of the decrement effect of wind speed and pressure and the adequacy of ventilation rate. Natural ventilation performance according to the parameters is evaluated by CFD simulation.

Simplified Prediction Method of Stack-Induced Pressure Distribution in High-rise Residential Buildings

Abstract This paper presents a simple prediction strategy for estimating the pressure distribution in high-rise residential buildings, using key parameters that affect the magnitude and distribution of stack pressure. The strategy is composed of two procedures: first, the stack pressure is predicted from parameters such as the height of the elevator shaft, the location of the neutral pressure level for each shaft, and the interior temperature of each shaft. Then, the pressure distribution of each floor is calculated using the equivalent leakage areas of the exterior and interior walls, by which finally the pressure difference across the exterior walls can be estimated. To verify the feasibility of this strategy, the predicted pressure differences across exterior walls were compared to measured data of a high-rise residential building with multiple elevator zoning. The results show that this strategy can predict pressure distribution quickly with satisfactory results for both the architectural designer and HVAC engineer.

Experimental Study on Insulation Performance and Condensation Characteristics of a Vacuum Insulated Glass Window

Abstrct Through a mock-up test the surface temperature distribution and condensation characteristics were analyzed for a vacuum insulated glass (VIG) window, manufactured through an in-vacuum method, and compared with a double-glazed (DG) window. The outside air temperature was -21.2°C for a VIG window, at which the inside surface condensation begins to occur, given an inside air temperature of 20°C and an inside relative humidity of 50%; thus, given the typical weather conditions for Seoul, a VIG window is not likely to have condensation. The surface temperatures of the VIG window were found to be approximately 4 K–6 K higher than those of the DG window. In the case of the VIG window, the surface temperature of the center of glass is higher than that of the frame, because the vacuum insulated glass (VIG) has a superior insulation performance compared with the frame. However, the surface temperature of the edge of the vacuum insulated glass is lower than that of the frame, by approximately 0.9 K–1.5 K. Thus, to reduce heat loss and improve condensation resistance, measures to reduce heat loss at the glass connection should be established and frames should be utilized that have insulation performance equal to or better than VIG.

Development of an evaluation strategy of hydronic balancing valves for radiant floor heating systems

In order to increase thermal comfort and energy efficiency, individual room control is highly recommended for radiant floor heating systems. For this reason, hydronic balancing is essential to provide the design flow rate to each branch circuit, which can be regarded as the ultimate goal of individual room control for radiant floor heating systems. In general, balancing valves are widely applied to hydronic circuits of radiant floor heating systems in common residential buildings, in order to achieve the purpose of hydronic balancing. This study aims to suggest an evaluation strategy of balancing valve performance for radiant floor heating systems. In the strategy, adjustment range and accuracy are evaluated by using the Kv value, in order to evaluate the balancing performance for practical applications of balancing valves. Additionally, the flow distribution by balancing valves was evaluated with the hydronic network simulation, by which flow quotients of hydronic circuits were investigated. Based on the evaluation strategy, the performances of six different balancing valves, which are applied to typical residential buildings, were successfully evaluated. Practical application : This study presents an evaluation strategy to evaluate the performance of hydronic balancing valves for radiant floor heating systems. The proposed evaluation strategy will be able to provide a method to analyse the impact of hydronic balancing and to determine suitable balancing valves for radiant floor heating systems in residential buildings. Therefore, it is expected that the results will be helpful to researchers for indoor environment, building service engineers, system designers, and those who want to analyse the hydronic control of radiant floor heating systems.

Corrections for minimizing solar profile prediction errors and methods for preventing direct glare on the workplane in blind control

As a means of improvement of environmental comfort in buildings with blind control, the objective of this study is to minimize solar profile prediction error for the purpose of preventing direct glare caused by the sunlight inlet in blind control. During the process of solar profile prediction, the main variables that cause prediction error of the solar profile were defined and problems from the prediction error were analysed. Surface orientation and time are significant factors that may cause error and glare during blind control. This research proposes and evaluates the correction methods and control strategy to minimize prediction error. In this research, the proposed correction methods and control strategy, which considers the surface orientation based on True North and potential time errors, could solve problems of direct glare caused by daylight inlet on the workplane, according to prediction errors of the solar profile. These methods could also be used to maximize daylight and solar heat gain, because the blocked area on windows could be minimized.