Hot Water Pipes Research Articles

다공질 장석으로 제조한 축열층의 열전도 특성

다공성 구조의 장석과 주택 시방기준으로 제작된 바닥 축열층 모르타르의 열적 특성과 소비전력을 비교하였다. 실험을 위해 온수관이 설치된 2개의 실대형 모형을 제작하였다. 자외선 열화상 온도와 온도센서를 이용하여 가열과 냉각과정에서 축열층의 온도변화를 모니터링하였다. 시험동의 축열층은 <TEX>$20-30^{\circ}C$</TEX> 구간의 온도 범위의 가열조건에서 <TEX>$2-3.5^{\circ}C$</TEX> 높은 온도를 보였고 목표 온도에 도달하는 시간이 단축되었다. 온수관에서 멀어질수록 <TEX>$4-4.8^{\circ}C$</TEX> 이상의 차이를 보였고 이는 장석 기반의 모르타르 축열층이 열적 평형에 빨리 도달하는 것을 지시한다. 가열 온도 <TEX>$30^{\circ}C$</TEX>를 기준으로 산정한 소비전력은 2.2배 차이를 보였고 단계별 온도 상승에서 소비전력은 66% 절감되었다. 냉각에서 시험동의 표면온도는 지속해서 <TEX>$2^{\circ}C$</TEX> 이상 높았고 축열로 인해 보일러의 재가동 시간이 연장되는 것을 고려하면 에너지 효율은 더 증가할 것이다. The temporal and spatial temperature distribution of the heat storage mortar made of porous feldspar was measured and the thermal properties and electricity consumption were analyzed. For the experiment, two real size chambers (control model and test model) with hot water pipes were constructed. Two large scale models with hot water pipes were constructed. The surface temperature change of the heat storage layer was remotely monitored during the heating and cooling process using infrared thermal imaging camera and temperature sensor. The temperature increased from <TEX>$20^{\circ}C$</TEX> to <TEX>$30^{\circ}C$</TEX> under the heating condition. The temperature of the heat storage layer of the test model was <TEX>$2.0-3.5^{\circ}C$</TEX> higher than the control model and the time to reach the target temperature was shortened. As the distance from the hot water pipe increased, the temperature gap increased from <TEX>$4.0^{\circ}C$</TEX> to <TEX>$4.8^{\circ}C$</TEX>. The power consumed until the surface temperature of the heat storage layer reached <TEX>$30^{\circ}C$</TEX> was 2.2 times that of the control model. From the heating experiment, the stepwise temperature and electricity consumption were calculated, and the electricity consumption of the heat storage layer of the test model was reduced by 66%. In the cooling experiment, the surface temperature of the heat storage layer of the test model was maintained <TEX>$2^{\circ}C$</TEX> higher than that of the control model. The heat storage effect of the porous feldspar mortar was confirmed by the temperature experiment. With considering that the time to reheat the heat storage layer is extended, the energy efficiency will be increased.

A study on Zone Heating Technology for Cherry Tomato by Using a Hot Water Pipe and Blowing Fan

In this study, a hot water pipe and a blowing fan were combined for developing zone heating technology for cherry tomato. The concept of this system was that hot air was firstly made by hot water pipe in one layer plastic duct and then a blowing fan made the hot air formed in a duct discharge through a duct hole to a shoot apex or a flower cluster which was temperature-sensitive part of cherry tomato. This system mainly consisted of hot water boiler, thermal tank, heat radiation plastic duct with the function of moving up and down electrically depending on the height of shoot apex. Developed system was applied to the cherry tomato greenhouse located in Jangam Chungcheongnamdo from Dec. 28, 2015 to Feb. 16, 2016 and compared with conventional entire space heating system of cherry tomato greenhouse and looked into cumulative yield for the estimate of growing state and energy saving rate from the conventional consumed energy. The result showed that cumulative yield was 3% higher and consumed energy was 32% lower than those of control greenhouse. The average temperature of shoot apex zone was 0.4~1.1℃ higher and the average relative humidity of shoot apex zone was 2,2~2.3% lower than those of entire space during night time in a shoot apex zone heating greenhouse and the average temperature of shoot apex zone was 0.7~1.4℃ lower and the relative humidity of shoot apex zone was 2.9~8.3% higher than those of entire space during night time in a entire space heating greenhouse.

Proposal of a PCM Underfloor Heating System Using a Web Construction Method

Apartment buildings in Korea have adopted underfloor heating systems using web construction methods based on concrete and hot water systems. However, since such systems consume significant amounts of energy for heating owing to their low thermal storage performance, it is necessary to develop a new system that can minimize energy consumption by improving concrete thermal storage performance. This study proposes a phase-change material (PCM) underfloor heating system to reduce energy consumption in apartment buildings. An optimal design for a PCM underfloor heating system is proposed, and thermal storage performance of the proposed system is evaluated experimentally. The temperature range of the PCM for underfloor heating is also calculated considering the proposed design and comfortable heating conditions for domestic apartment buildings. Results indicate that a PCM underfloor heating system can be constructed in the following order: (1) a 210 mm concrete slab, (2) a 20 mm cushioning material, (3) 40 mm of mortar including a 10 mm PCM thermal storage container, and (4) 40 mm of finishing mortar including wire mesh and hot water pipes. The temperature range of the PCM used for underfloor heating in domestic apartment buildings is 32–45°C. Experimental tests reveal that thermal storage performance of underfloor heating systems that apply 35, 37, 41, and 44°C as representative PCM temperatures is superior to existing systems.

온수배관을 이용한 시설딸기 부분난방기술 개발

온수배관을 이용한 시설딸기 부분난방기술 개발

An energy-based sparse representation of ultrasonic guided-waves for online damage detection of pipelines under varying environmental and operational conditions

This work addresses the main challenges in real-world application of guided-waves for damage detection of pipelines, namely their complex nature and sensitivity to environmental and operational conditions (EOCs). Different propagation characteristics of the wave modes, their distinctive sensitivities to different types and ranges of EOCs, and to different damage scenarios, make the interpretation of diffuse-field guided-wave signals a challenging task. This paper proposes an unsupervised feature-extraction method for online damage detection of pipelines under varying EOCs. The objective is to simplify diffuse-field guided-wave signals to a sparse subset of the arrivals that contains the majority of the energy carried by the signal. We show that such a subset is less affected by EOCs compared to the complete time-traces of the signals. Moreover, it is shown that the effects of damage on the energy of this subset suppress those of EOCs. A set of signals from the undamaged state of a pipe are used as reference records. The reference dataset is used to extract the aforementioned sparse representation. During the monitoring stage, the sparse subset, representing the undamaged pipe, will not accurately reconstruct the energy of a signal from a damaged pipe. In other words, such a sparse representation of guided-waves is sensitive to occurrence of damage. Therefore, the energy estimation errors are used as damage-sensitive features for damage detection purposes. A diverse set of experimental analyses are conducted to verify the hypotheses of the proposed feature-extraction approach, and to validate the detection performance of the damage-sensitive features. The empirical validation of the proposed method includes (1) detecting a structural abnormality in an aluminum pipe, under varying temperature at different ranges, (2) detecting multiple small damages of different types, at different locations, in a steel pipe, under varying temperature, (3) detecting a structural abnormality in an operating hot-water piping system, under multiple varying EOCs, such as temperature, water flow rate, and inner pressure; and (4) detecting a structural abnormality as the ratio of the damaged pipe's signals in the reference dataset increases.

District Heating Safety Issues: Interactions Between Grounding Systems and Thermal Installations

The structure of a district heating network lends itself to interactions among the grounding system of the generating plant, and those of the users, with the possibility that hazardous induced voltages may occur on the latter. Hazards are possible due to the bonding of the heating system pipes to customers grounding systems, as well as to possible high values of fault currents. These electrical safety issues due to grounding electrode interactions have been so far poorly treated in technical literature. District heating pipes are generally dielectrically separated in segments by means of insulating joints. A deeper analysis of such joints shows that the hot water circulating in the pipes may bypass their insulation, rendering the effectiveness of the dielectric separation strongly dependent on the joint geometry, and on the water electrical conductivity. The authors propose possible schemes for the hot water pipes connections, and discuss their efficiency based upon the electrical configuration of the generation plant. An experimental verification procedure to assess the electrical safety of the district heating system is also proposed.

Hydraulic and Thermal Conductivities of Kaolin–Silica Mixtures under Different Consolidation Stresses

Stable backfill materials for the heat sensitive structures of buried power cables, hot water pipes, and gas pipelines are suggested to have low permeability and high heat transfer characteristics. The hydraulic and thermal conductivities of backfill materials or clay liners are important parameters in proper design and construction of geotechnical structures involved with heat transfers. In this study, to investigate the optimal natural backfill or liner materials, thermal and hydraulic conductivities of kaolin–silica mixtures examined based on the results from laboratory tests under different consolidation conditions. From the experiment results, the thermal conductivity increases while hydraulic conductivity decreases with increasing density during consolidation process. As a result, back-fill materials with high kaolin content under low consolidation stress were desirable materials for burial of heat sensitive structures.

Outbreak of six cases of nosocomial Legionella pneumophila pneumonia

To describe the clinical characteristics, diagnosis, treatment and the causes of outbreak of nosocomial pneumonia due to Legionella pneumophila. The medical records of 6 cases of nosocomial Legionella pneumophila pneumonia were retrospectively reviewed, and the clinical data of clinical presentation, treatment, and etiologic diagnosis were analyzed. The 6 patients were health care providers of the Department of Respiratory and Critical Care Medicine of the Affiliated Hospital of Logistics University of PAPF. There were 5 female and 1 male patients, aged 23 to 27 years. The diagnosis of Legionella pneumonia was made based on a positive Legionella urinary I antigen test. In all the 6 cases, the disease was attributable to inhaling contaminated aerosols produced by the air conditioning system in our hospital. All the 6 patients presented with fever of 37.5-39 °C, and productive cough. One patient had anorexia, dyspnoea, and pleuritic chest pain, while headache was reported in 3 patients. Physical examinations revealed lung rales in 3 patients. Single or multiple patchy infiltrates were found on Chest CT in all patients. However, the typical extrapulmonary manifestations of Legionnaires' disease, including relative bradycardia, hyponatremia, hypophosphatemia and diarrhea, were not present in the 6 patients. Neither neurological abnormalities nor renal involvement were observed. Our data demonstrated that Legionella pneumonia may be mild with atypical laboratory findings and clinical manifestations, with fever, cough, chest tightness, headache, etc. The radiologic manifestations of Legionella pneumonia were single or multiple patchy infiltrates, similar to those of viral pneumonia, and therefore their differential diagnosis was needed. Legionella pneumophila can outbreak through the respiratory tract, in public places with central air-conditioning system, hot water piping systems and hospitals, and therefore microbiological monitoring, cleaning and disinfection of the water system was required for prevention of the outbreaks of Legionnaires' disease.

Robust ultrasonic damage detection under complex environmental conditions using singular value decomposition

Guided wave ultrasonics is an attractive monitoring technique for damage diagnosis in large-scale plate and pipe structures. Damage can be detected by comparing incoming records with baseline records collected on intact structure. However, during long-term monitoring, environmental and operational conditions often vary significantly and produce large changes in the ultrasonic signals, thereby challenging the baseline comparison based damage detection. Researchers developed temperature compensation methods to eliminate the effects of temperature variation, but they have limitations in practical implementations.In this paper, we develop a robust damage detection method based on singular value decomposition (SVD). We show that the orthogonality of singular vectors ensures that the effect of damage and that of environmental and operational variations are separated into different singular vectors. We report on our field ultrasonic monitoring of a 273.05mm outer diameter pipe segment, which belongs to a hot water piping system in continuous operation. We demonstrate the efficacy of our method on experimental pitch–catch records collected during seven months. We show that our method accurately detects the presence of a mass scatterer, and is robust to the environmental and operational variations exhibited in the practical system.

Characterization of Scale Formed in Drinking Water and Hot Water Pipes in the Taliouine Downtown—Morocco

This paper presents the results of a comprehensive study of water scale found in water distribution system of Taliouine city in the south of Morocco. Physico-chemical properties of drinking water supplied to the city were evaluated. The data showed a high level of soluble salt in water. Concentrations were calcium 108 - 143 mg/1, magnesium 80 - 96 mg/1, bicarbonate 660 - 750 mg/l and hardness degree 660 - 690 mg CaCO3/l. The water samples contain high amounts of minerals in the form of ions, especially the metals calcium and bicarbonate, which precipitated out and caused problems in water conducting or storing vessels like pipes. Scales were removed from the inside of two old pipes which transported drinking and hot water in the downtown of Taliouine city. Scale samples were investigated by XRF, XRD, SEM, DTA, TGA and SEM’s analytical techniques. This study was able to identify scales formed in pipes of water distribution systems. It was found that water scale in this city contains 53% of calcium oxide and 43% of organic matter. The XRD and SEM results revealed that calcite was the main crystalline structure in drinking water scale. Nevertheless, scale deposited in hot water pipe is well crystalline with peaks corresponding mostly to aragonite (88%) along with calcite (12%). The thermal behavior of scale samples confirms that calcium carbonate was the main compound in the scale samples. Further studies are needed to find an efficient antiscale in drinking water of this city.

Heat and Mass Transfer in a Wetted Thermal Insulation of hot Water Pipes Operating Under Flooding Conditions

We present the results of numerical simulation of the thermal regimes of hot water pipes under flooding conditions with account for evaporation and diffusion of steam in a wetted thermal insulation. The extents of heat losses by hot water pipes under these conditions have been revealed. The contributions of evaporation and steam diffusion effects to the total heat losses are shown. The necessity of taking into account the nonstationarity of transfer processes and of the values of volume fractions of moisture and steam in the structure of a wetted thermal insulation layer in modeling thermal regimes of hot water pipes under flooding conditions has been proven.

Reducing CO2 emissions in the individual hot water circulation piping system

Central hot water piping systems are used in large lodging buildings (e.g. hotels, dormitories, etc.) for comfort and convenience. However, the big problem to this type of system is that once the hot water leaves the storage tank and travels through the system piping, the water temperature drops due to the travel distance and ambient air temperature. Because of this drop in temperature, users need to wait for the undesirable cool water to flow out of the system before the desired hot water starts flowing out of the system. The ideal solution to this problem is to reheat the undesirable (cooled) water in the system by the use of an individual hot water circulating system. This study focuses on water saving and energy consumption in the individual hot water circulating system. The results show energy consumption is 50% less than the non-circulating central hot water system. Three parameters in wasted water demand, electric consumption, and heating source consumption were considered to transfer them with CO2 transfer coefficient to estimate the reducing CO2 emission. The hot water circulation system presents the benefits of water and energy saving, and reduction of CO2 emission, but the piping connection should be improved for easy installation in the existed buildings in the future.

Mycobacterium avium Complex in Day Care Hot Water Systems, and Persistence of Live Cells and DNA in Hot Water Pipes

The Mycobacterium avium complex (MAC) is a group of opportunistic human pathogens that may thrive in engineered water systems. MAC has been shown to occur in drinking water supplies based on surface water, but less is known about the occurrence and persistence of live cells and DNA in public hot water systems based on groundwater. In this study, we examined the occurrence of MAC in hot water systems of public day care centers and determined the persistence of live and dead M. avium cells and naked DNA in model systems with the modern plumbing material cross-linked polyethylene (PEX). The occurrence of MAC and co-occurrence of Legionella spp. and Legionella pneumophila were determined using cultivation and qPCR. Co-occurrences of MAC and Legionella were detected in water and/or biofilms in all hot water systems at temperatures between 40 and 54°C. Moderate correlations were observed between abundance of culturable MAC and that of MAC genome copies, and between MAC and total eubacterial genome copies. No quantitative relationship was observed between occurrence of Legionella and that of MAC. Persistence in hot water of live and dead M. avium cells and naked DNA was studied using PEX laboratory model systems at 44°C. Naked DNA and DNA in dead M. avium cells persisted for weeks. Live M. avium increased tenfold in water and biofilms on PEX. The results suggest that water and biofilms in groundwater-based hot water systems can constitute reservoirs of MAC, and that amplifiable naked DNA is relatively short-lived, whereas PEX plumbing material supports persistence and proliferation of M. avium.

Modelling and simulation of a hybrid solar heating system for greenhouse applications using Matlab/Simulink

Solar energy is a major renewable energy source and hybrid solar systems are gaining increased academic and industrial attention due to the unique advantages they offer. In this paper, a mathematical model has been developed to investigate the thermal behavior of a greenhouse heated by a hybrid solar collector system. This hybrid system contains an evacuated tube solar heat collector unit, an auxiliary fossil fuel heating unit, a hot water storage unit, control and piping units. A Matlab/Simulink based model and software has been developed to predict the storage water temperature, greenhouse indoor temperature and the amount of auxiliary fuel, as a function of various design parameters of the greenhouse such as location, dimensions, and meteorological data of the region. As a case study, a greenhouse located in Şanlıurfa/Turkey has been simulated based on recent meteorological data and aforementioned hybrid system. The results of simulations performed on an annual basis indicate that revising the existing fossil fuel system with the proposed hybrid system, is economically feasible for most cases, however it requires a slightly longer payback period than expected. On the other hand, by reducing the greenhouse gas emissions significantly, it has a considerable positive environmental impact. The developed dynamic simulation method can be further used for designing heating systems for various solar greenhouses and optimizing the solar collector and thermal storage sizes.

FREEZE PROTECTION METHOD USING HOT WATER FOR PASSIVE SOLAR WATER HEATING SYSTEM

In the present work, a new freeze protection method is introduced with intended applications for passive solar water heaters. Though electro-thermal wire heat tracing is popularly used to prevent freezing with subsequent risk of burst, this approach is problematic due to resistance heater failure and excessive electric power consumption. In the experimental device, hot water in thermal storage tank is used to heat the outlet pipe from the tank when the surface temperature of the pipe falls lower than a pre-determined set point. The cold water pipe to the thermal storage tank is installed in direct contact with the hot water pipe, controlling its temperature by conduction with the hot water pipe.

Constructal design of multiple heat sources in a square-shaped fin

A new study area of constructal theory is presented by applying constructal design on multiple heat sources which connected to and cooled in a square-shaped fin. Analyzing the optimal location of the heat sources in the fin for several configurations is the primary goal of this study. According to the constructal theory, favorable distribution of the heat sources is achieved by minimizing the global thermal resistance of the fin body. Since the heat sources might be contemplated as heat-generating electronic bodies or hot-water pipes, two boundary conditions of uniform heat flux and uniform temperature are considered for the heat sources. The minimization of the thermal resistance in the uniform heat flux and uniform temperature cases leads to the minimization of the hot spot temperature and the maximization of the total heat removal, respectively. Temperature fields in the square-shaped fin are calculated using a finite element approach of MATLAB PDE Toolbox. The optimized configurations are numerically compared with each other. It is shown that the most commonly used configurations of the heat sources in a cooling industry are unfavorable and must be avoided. Favorable configurations such as triangular arrangement of heat sources are proposed to replace the unfavorable configurations.

2A1-O04 空気圧駆動式3体節イモムシ型管内走行ロボット(特殊移動ロボット(1))

This paper deals with a new inspection robot imitating a green caterpillar. Gas or water pipes for individual or corporate houses and boilers or hot water pipes for industries are settled in the ground or in the narrow spaces and some of them are covered by casings or hard heat insulators. So, it is very difficult to inspect from outside of the pipe. However, we are easy to inspect the pipe from inside of the pipe. Conventional inspection robots imitating an earthworm and inchworm could not move in different diameter pipe and could not generate large traction force. The green caterpillar sticks a passage such as the leaf by its prolegs. The new inspection robot can move in the pipe whose diameters are from 70 mm to 100 mm, generating the traction force of 17.6 N.

Fuel cells and energy networks of electricity, heat, and hydrogen: A demonstration in hydrogen-fueled apartments

A demonstration was performed to evaluate our proposal of a residential energy system based on fuel cells and energy networks of electricity, hot water, and hydrogen. The demonstration was conducted from April 2007 to March 2009 in a small apartment building constructed for experimental purposes in Osaka City. Three small proton exchange membrane fuel cells were installed, and the electricity and hot water from the fuel cells were shared among 6 units via an internal electricity grid and hot water pipe. A hydrogen production facility, a small storage device, and a hydrogen pipe were installed to supply hydrogen to the fuel cells. Six families went about their normal daily lives using this system. The energy flow from hydrogen production to consumption was demonstrated. The results of fuel cell operation, energy supply, and energy demand, as well as an analysis of primary energy saving and CO2 emission mitigation are presented.

Radical-Mediated Graft Modification of Polyethylene Models with Vinyltrimethoxysilane: A Fundamental Study

Cross-linked polyethylenes have widespread applications such as insulators for current-carrying wires/cables and for hot water pipes. Industrially, cross-linked polyethylene can be prepared via the radical-initiated grafting of polyethylene with vinyltrimethoxysilane (VTMS) followed by moisture-induced cross-linking. The efficiency of the grafting reaction is not optimal: (1) a large portion of the VTMS remains unreacted and (2) controlling the distribution and extent of grafting is difficult. We present new contributions to the fundamental understanding of grafting reactions with VTMS on polymeric models (dodecane and heptane) as to the effect of phenyllithium capping reaction time on the analyses, the origin of the observation of multiple grafts, and the regiochemistry of the multiple graft products.

Energy supply performance and environmental load‐reduction effect of a cogeneration system for an apartment building using distributed heat storage technology

AbstractIn order to make distributed generation systems for apartment buildings economically viable, it is essential to develop an efficient and low‐cost heat supply system. We are developing a new cogeneration system (Neighboring CoGeneration system: NCG system). The key concept of this system is to install a heat storage unit for the hot water supply, floor heating, and bath heating in each house, and to connect the heat storage units by a single‐loop hot water pipe. The system leads to time leveling of the total heat supply and reduced installation costs. Furthermore, it is expected that the cogeneration can operate according to electrical demand because of the large heat storage capacity of the system. In this study, a dynamic simulation model is developed to evaluate the performance and environmental load‐reduction effect of the NCG system for 50 households. The results show that the NCG system can supply sufficient heat for peak demand in winter and reduce annual CO2 emissions by 23% on average. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 42(8): 745–757, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.20376