Current study is aimed at making the most appropriate design considering the dynamic energy, exergy and economic analysis of Ground Source Heat Pumps (GSHP). The energy required to heat and to cool a ...200 m2 office in Istanbul is determined, and based on these data, the entering and leaving water and soil temperatures of horizontal Ground Heat Exchanger (GHE) are obtained numerically for a ten-year period with realistic boundary conditions using meteorological data. The results obtained from the numerical study are confirmed by GHE experimental setup built in Yıldız Technical University. The variations of COP, second-law efficiency and exergy destruction of each component of GSHP at both seasons of the first, fifth and tenth years are obtained for Radiant Wall Panel Unit (RW-PU), Floor Heating + Fan-Coil Unit (FH-FCU) and Radiator + Fan-Coil Unit (R-FCU) systems. At the end of the 10-year dynamic simulation period of the GSHP system, the average values of COP and second law efficiency for RW-PU, FH-FCU and R-FCU are found as 4.01, 3.37, 3.01, and 39.29%, 38.04%, 36.63%, respectively. Furthermore, considering the initial investment and operational costs of RW-PU, FH-FCU and R-FCU systems integrated into the GSHP system, an objective function is defined as an optimization parameter.
•Obtaining the steady periodic temperature profile for ground heat exchanger sizing.•Long-term energy, exergy and economic analysis of GSHP are performed.•RW-PU, FC-FCU and R-FCU systems are employed for living space conditioning.•An objective function is defined as an optimization parameter.•Country’s electricity tariff and its increase rate are important for GSHP investment.
Mean radiant temperature (MRT) is one of the six primary factors that determine thermal comfort in a given thermal environment. In this study, the average radiant temperature was determined using a ...calculation method based on the surrounding surface temperatures and view factors. The present study specifically investigated the use of calculated radiant temperature, compared to measured radiant temperature, for predicting the mean vote (PMV) and percentage of dissatisfied (PPD) comfort parameters. The method was validated by the experimental measurements via the black sphere thermometer at five different reference points in a test room, including radiant panels on the ceiling and walls. By using global thermometer measurements, the proposed approach achieved a high degree of compatibility and an accuracy of 0.17 °C, which was the difference between calculated and measured values. The results demonstrated the reliability of the procedure using view factors and surrounding surface temperatures to calculate the radiant temperature in the designated test room; here, a straightforward method for evaluating the thermal conditions of an office room and determining the optimal location of an air temperature sensor in PMV-controlled radiant systems was also proposed. This study contributes to the increasing field of research on thermal comfort and offers knowledge that is beneficial for the design and optimization of indoor environments.
•Obtaining the steady periodic temperature profile for ground heat exchanger sizing.•The effects of burial depth, distance between pipes and surface effects on soil temperature.•Long term simulation ...of the variation of fluid inlet and outlet temperatures and soil temperature.•Long term hourly analysis of an office in Istanbul.
A ground heat exchanger is the most important part of a ground source heat pump system. Soil properties and ground heat exchanger performance strongly depend on soil temperature profile and vary with time and space. Also, soil temperature profile is a function of heat transfer rate extracted or transferred to soil. Studies in the literature either use the unaffected soil temperature obtained from meteorological data or fail to run for long time periods to obtain a steady periodic soil temperature profile and over-predict the ground heat exchanger performance. Therefore, steady periodic temperature profile should be used for sizing ground heat exchanger for efficient operation of ground source heat pumps for longer periods of time. Experimental studies are carried out on a ground-source heat pump established at Yıldız Technical University, Davutpaşa Campus and the newly developed numerical model is validated with experimental results. For the numerical study, the hourly required heat load of a 200 m2 office in Istanbul during the heating season is calculated by using HAP software. The transient soil temperature profile is obtained numerically for longer periods of time with realistic boundary conditions using meteorological data. The fluid inlet temperatures equivalent to the hourly need for heating load of the office during the heating season are simulated for a ten-year period in accordance with the different heat amounts extracted from unit pipe length in soil (21, 10.5 and 7 W/m). The effects of burial depth, distance between pipes and surface effects on soil temperature are also investigated. Horizontal and vertical temperature distribution in soil at the beginning (November 10th), middle (January 21st) and end (April 3rd) of the first, fifth and tenth years are represented.
A ground heat exchanger is the essential part of a ground source heat pump system. The soil temperature profile strongly influences soil properties and ground heat exchanger, which vary with time and ...space. The soil temperature profile is also a function of the heat transfer rate extracted from/or transferred to soil. Although there are several studies on the sizing and selection of ground heat exchangers, they either use the unchanged soil temperature obtained from meteorological data or do not run for long time periods to obtain a steady periodic soil temperature profile and, thus, over-predict the ground heat exchanger performance. The aim of this study is to obtain transient soil temperature profile of a parallel pipe horizontal ground heat exchanger by considering various system parameters with realistic boundary and operating conditions using meteorological and hourly building data. Experimental results have been obtained from a GSHP system established at Yıldız Technical University and compared with the results of numerical analysis. For a case study, the hourly required heating and cooling loads of a 200 m2 office in Istanbul all year round are calculated by using HAP software. The fluid inlet temperatures equivalent to the hourly need for heating and cooling loads of office throughout the year have been simulated for a ten-year period in accordance with the different heat amounts extracted from soil or transferred to soil per unit pipe length. The effects of burial depth, pipe spacing and surface effects on soil temperature are also investigated. The horizontal and vertical temperature distribution in soil at the beginning, middle and end of heating and cooling seasons of first, fifth and tenth years are represented. Considering initial and operating costs, a reference function is defined as an optimization parameter. The effects of the increase rate in electricity prices, number of parallel pipes (NPT), burial depth, pipe spacing, pipe diameter and pipe length on reference function are investigated.
•The numeral results reveal a good agreement with the experiments.•Effects of pipe location and NPT on the performance of GSHP are investigated.•Higher COP values are obtained when the pipes are ...buried in soil under the foundation.•A reference function is defined as an optimization parameter.•Effects of technical and economical parameters on reference function are studied.
The aim of this work is to improve the performance of Ground-Source Heat Pumps (GSHPs) by placing the heat exchanger pipes in the soil under the building foundation and in the building foundation reconstructed in Turkey. In this scope, firstly, experimental studies have been performed on horizontal parallel pipes buried in soil under the foundation of the 2400 m2 Central Laboratory building, which was newly built at Yıldız Technical University. A comparison between the results of the experimental and newly developed numerical model is presented. Then, a full-scale numerical model for a shopping mall is developed based on the pipe location (soil and concrete layer), Numbers of Parallel Tube (NPTs) and different condensation temperatures in the heating season. The results show that the COP of GSHP when the pipes are buried in the soil under the building foundation is greater than when the pipes are buried in the building foundation. Furthermore, considering capital investment and operational costs, a reference function is defined as an optimization parameter. The effects of the pipe location, increasing rates in electricity prices and NPTs on reference function are investigated. For higher NPT values, locating the pipes in the foundation gives higher values of the reference function while for lower NPT values it is vice versa.
Snow and ice forming on the entrance and exit driveways of underground car parks of buildings brings serious difficulties and risks in safe parking for vehicles in winter. Even though traditional ...methods such as chemical salt and snow plowing reduce slippery conditions on driveways, they also result in infrastructure- and environment-related damages. Hydronic heating is an alternative way to prevent snow and ice forming; thereby, the hydronic heating driveway (HHD) is a promising technique for energy-efficient and environment-friendly solutions. This study presents a time-dependent three-dimensional numerical heat transfer model for HHD applications with realistic boundary conditions and meteorological data in the MATLAB environment. After developing the numerical heat transfer model, the model is applied to a case study in Istanbul, Turkey and followed by an economic comparison with the commercial electrically-heated driveways (EHD) method that is applied in two different ways; applying the electric cables in (i) whole driveway and (ii) only tire tracks. Different escalation rates in natural gas and electricity, hot fluid inlet temperature, air temperature, and the number of parallel pipes are the main parameters in the case study. Results show that the decrease in pipe spacing drops the investment cost term but it needs a higher supplied fluid temperature for anti-icing, and therefore the operating cost term increases. Among other cases was the number of parallel pipes, with 50 being the most economically feasible solution for all air temperatures ranging from 0 °C to −10 °C. The economic comparison shows that the EHD with only tire tracks has the minimum total cost as it significantly decreased both the operating and investment cost terms. In case of an anti-icing requirement on the whole road surface, the HHD system was found to be preferable to the EHD whole driveway scenario at air temperatures of 0 °C and −5 °C, while it is more beneficial only for the high electricity escalation rates at the ambient temperature of −10 °C.
This study investigated the impact of two types of internal blinds on the indoor thermal environment of a highly glazed office room in Istanbul during summer. The research examined four ...configurations: (i) no blinds, (ii) roller blinds, (iii) layered roller blinds in night mode and (iv) layered roller blinds in day mode. Measurements of air velocity, average radiation temperature, air temperature and relative humidity were conducted to assess thermal comfort. The findings revealed that internal blinds significantly influence thermal comfort in radiantly cooled office spaces during summer. Without blinds, the indoor environment only met ISO 7730 comfort category C, with average predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD) values of 0.6 and 12.5%, respectively. However, with internal blinds, comfort categories A and B were achieved, resulting in improved thermal comfort levels, with average PMV and PPD values ranging from 0.2 to 0.3 and 6% to 7.5%, respectively. Roller blinds, in particular, proved highly effective in enhancing thermal comfort and reducing mean radiant and indoor air temperatures in highly glazed radiant cooling offices. This demonstrated their energy-efficient potential for improving indoor thermal comfort.
•The effect of different geometrical and flow conditions for microchannels with VGs.•Thermal-hydraulic performance of the microchannels with VGs is examined in details.•Response Surface Methodology ...is adopted for optimization work.•Pareto optimal solution is obtained from Multi-Objective Genetic Algorithm method.•Predictive sensitivity of the empirical correlations proposed for Nu and f is fairly well.
In this study, delta winglet-type vortex generators, widely used in conventional macro channels and proven to be effective, are used in microchannels to increase their heat transfer capacities. The effects of vortex generators on heat transfer and pressure loss characteristics are studied numerically for different angles of attack, vortex generator arrangement type, the transverse and longitudinal distance between vortex generators, vortex generator length and height, and different Reynolds numbers. The thermal and hydraulic characteristics are presented as the Nusselt number, the friction factor, and the performance evaluation criteria number (PEC) that takes into account the heat transfer enhancement and the corresponding increase in pressure loss. The variation of Nu/Nu0, f/f0, and PEC are found to be in the range of 1.03–1.87, 1.04–1.8, and 0.92–1.62, respectively. A multi-objective optimization study are performed with the response surface methodology analysis to see how different parameters affect heat transfer and pressure loss and to determine the most optimum design. Besides, local sensitivity analysis study is carried out through the RSM, and water inlet velocity for heat transfer enhancement is found to be the most effective parameter. Among the geometric parameters, vortex generator height is determined as the most effective factor. Finally, practical Nusselt number and friction factor correlations taking many parameters into account are proposed to be able to compare the results of other researchers, and for engineers designing microchannel cooling systems.
Hydronic radiant systems, which provide a thermal comfort environment, come to the fore in different building applications due to their energy saving potential and being integrated with renewable ...energy systems. The aim of this study is to present a full-scale experiment to compare the thermal comfort performances of radiant ceiling, wall and wall + ceiling systems coupled ground source heat pump and direct expansion fan coil system implemented in Yildiz Technical University Science and Technology Application and Research Center, Istanbul, Turkey. Air velocity, horizontal and vertical air temperature differences, mean radiant temperature and humidity values, which are four physical parameters that can affect the thermal satisfaction of office workers for 9 different experimental conditions, are measured for fan coil and all radiant systems. The results indicate that vertical temperature differences between ankle and head level vary from 0.9 °C to 1.4 °C for both fan coil system and all radiant system configurations in different location of the test room. Acceptable overall comfort in indoor environments Class A only showed stable performance with an average of 0.12 PMV and 5.3 % PPD when ceiling + wall radiant panels were actively cooled. The result shows that the difference between room air temperature and room operating temperature varies between 0.45 °C and 0.6 °C when cooling loads are met by radiant systems. This may not make it possible to use indoor air temperature instead of indoor operating temperature in the control of radiant systems. Moreover, the thermal environment of the radiant system are more uniform than fan coil system due to low air temperature stratification, air velocity and small differences between mean radiant temperature and indoor air temperature.
•Ground heat exchangers were implemented in both ground and concrete layers.•A new ground source heat pump method is proposed for building foundation.•A new numerical model is developed for 3-D ...temperature distribution.•Both layers give satisfying results while the ground has 19% better performance.
The current study proposes a novel method with the experimental and numerical studies for the ground source heat pumps, which are known as environment-friendly and efficient heating & cooling systems to overcome their economic drawbacks in the applied engineering operations. The experimental studies are carried out in the newly built Central Laboratory of Yıldız Technical University, Davutpaşa Campus, Istanbul, Turkey. The long parallel heat exchanger pipes are placed in two different layers of the ground that are (1) under the building foundation (ground layer), and (2) in the building foundation (concrete layer), respectively. Besides, a unique numerical model is developed in MATLAB environment to obtain temperature distributions in ground and concrete layers. Then, the numerical outputs are validated with the observed experimental results. The daily average of the energy amount extracted from the Ground and Concrete Loops was found as 5.51 and 4.63 kWh/day, respectively. The results are found satisfying for real applications in the building foundations.
