Horizontal Temperature Distribution Research Articles

Effect of Compartment Height with Fire Source on Horizontal Vent Flow and Temperature Distribution

The effect of compartment height with a fire source on the horizontal vent flow and temperature distribution was numerically investigated. Two compartment heights were examined, namely 1.1 m (H1.1) and 5.5 m (H5.5). Horizontal vent areas were set at 1% (HV01) and 10% (HV10) of the floor area, and fire sources were positioned at the center (FSC) and side (FSS). H1.1 exhibited a larger mass flow rate and higher velocity of vent flow than H5.5 for FSC cases with HV01 and HV10. In the case of HV01 with FSS, the mass flow rates between H1.1 and H5.5 were comparable. However, in the case o f HV10 w ith F SS, H5.5 d emonstrated a larger m ass flow r ate than H 1.1. V ent flow v elocities a ppeared similar between H1.1 and H5.5 for FSS cases with both HV01 and HV10. Meanwhile, H1.1 exhibited a higher temperature distribution than H5.5 for HV01 cases with FSC and FSS. For HV10 with FSC, H5.5 showed a higher temperature distribution than H1.1. Conversely, for HV10 with FSS, the opposite trend was observed. The previous correlation overestimated the results of the present numerical simulation regarding the fire plume centerline temperature rise. It was speculated that mixing within the compartment affected the trend of fire plume centerline temperature rise.

Finite elements simulation MHD free convection in a rectangular embedded corrugated rods cavity filled with CuO/water nanofluid

The convective heat transfer and fluid is investigated in a rectangle chamber along with corrugated heated rods. For preferable novelties, this study considered porous media, micropolar fluid and an inclined magnetic field effect. The physical illustrations of nanofluid flow is assimilated in terms of differential equations. We use the finite element approach to tackle the fluid flow and heat transfer in rectangular chamber. Flow regulating parameters are Rayleigh number, Darcy number and Hartman number. The horizontal and vertical velocities and temperature distribution are provided through the use of contour plots and line graphs. The results show that heat transmission rates increase due to the increasing values of Hartmann number. Because Lorentz forces are resistive, the velocity profile tends to flatten down as long as Hartman number increases. The Nusselt number and velocity profile have greater values around the heat boundaries.

Horizontal Distribution of Temperature Effect in Rubberized Concrete Pavement: A Case Study

Temperature distribution and the deformation behavior under temperature are important parameters in the design and evaluation of concrete pavements. In this paper, in order to study the horizontal distribution of the temperature effect on rubberized concrete pavement (RCP), the distribution differences of temperature, temperature gradient and strain at different horizontal locations were analyzed based on fiber Bragg grating test technology. The relationships between temperature and strain and between temperature gradient and strain were also investigated. The results show that within a cycle of temperature or temperature gradient change, the time of temperature increase or temperature gradient increase is only 1/4 of the whole cycle, significantly less than the time of the temperature or temperature gradient decrease. Comparing the center, edges and corner of the pavement, the horizontal distribution of temperature and temperature gradients in the RCP is uneven, and the greatest negative temperature gradient is experienced at the corner of the pavement, which is 25 °C·m−1 greater than the temperature gradient at the center. The negative temperature gradient at the corner of the concrete pavement exacerbates the bottom deformation at the center and edge of the pavement, especially in the X-axis direction at the center and in the Y-axis and Z-axis directions at the edge. The relationships between temperature and horizontal strain at the center and edge of the RCP have a significant hysteresis effect and are markedly stronger than those at the corner. Moreover, when the temperature gradient is less than −23.4 °C·m−1 or greater than 14.5 °C·m−1, the curling effect at the edge of the RCP is more obvious.

Experimental study on heating performance of micro-holes radiant plate under different installation types in severe cold regions

In order to alleviate energy shortage and maintain comfortable indoor environment, radiant air conditioning system is widely used. This paper designs and produces a miniaturized micro-holes radiant plate, which has the characteristics of orifice plate air supply and radiant heat transfer. The micro-holes radiant plate can be installation on the ceiling or sidewall without adding dynamics system and piping system. In order to explore the heating performance of the micro-holes radiant plate under different installation types, an experimental bench of air source heat pump micro-holes radiant plate heating system was built in Harbin, China, for laboratory heating. The experimental results showed that the indoor average temperature under various installation types could basically meet the set requirements, and the deviation was within 1 °C. The indoor horizontal temperature distribution was relatively uniform, and the temperature difference of each measuring point was less than 2 °C. The indoor vertical temperature difference was the smallest under the installation type with sidewall 50 mm from the ground at only 2.68 °C in the sitting position and 3.14 °C in the standing position, which meet China and ASHRAE standards. The ratio of the radiant heat transfer quantity under the sidewall heating was about 60 %, while the ratio under the ceiling heating was only about 30 %. The maximum ratio of the radiant heat transfer quantity was close to 70 % under the installation type with sidewall 50 mm from the ground. The experimental results provide theoretical support for the design and operation of air conditioning systems in severe cold regions.

Effects of Duct Height and Fire Location on Fire Phenomena of Enclosure with Two Horizontal Vents Installed on Ceiling

The effects of duct height (DH) and fire location (FL) in an enclosure on the mass flow rate and flow pattern of horizontal vent (HV) flow and temperature distribution in the enclosure were investigated through numerical simulations under the condition that two HVs were installed on the ceiling of the enclosure. To evaluate the effect of DH, DHs of HV1 were set to 0.19 m (HV1_DH0.19) and 0.05 m (HV1_DH0.05) under the condition that DH of HV2 was 0.05 m (HV2_DH0.05). The effect of FL was evaluated in three cases where the fire sources were located in the center of the floor (F LC), below HV1 (F L1), and below HV2 (F L2). With respect to the DH effect, the total mass flow rate of the vent flow was slightly higher and temperature was slightly lower in the case of HV1_DH0.19 than that in the case of HV1_DH0.05. However, considering the error bars, the effect of DH in this numerical simulation condition was considered to be insignificant. Furthermore, bidirectional flow patterns appeared in HV1 and HV2 in both DH conditions. Meanwhile, with respect to the FL effect, a bidirectional flow dominated by the mass flow rate of outflow occurred in the HV where the fire source was located, and a unidirectional inflow dominated by the mass flow rate of inflow occurred in the HV where the fire source was not located. The total mass flow rates of FL1 and FL2 conditions were similar, which were higher than those of FLC condition. The temperature was higher in FLC than those in FL1 and FL2. This was due to the small mass flow rate through the HV in the FLC. Meanwhile, an increasing trend of the temperature with the rising measurement height from the floor was observed at most of the temperature measurement points. However, when the fire source was located below HV1 and HV2, as the height from the floor increased, the temperature decreased and the overall temperature was low at the temperature measurement points below the vent where the fire source was not located. This trend was attributed to the occurrence of a strong unidirectional inflow wherein a large volume of low-temperature air flowed into the enclosure from the HV where the fire source was not located.

Full-scale experimental study on thermal smoke movement characteristics in an indoor pedestrian street

Indoor pedestrian street, a common architecture scheme, brings both convenience and fire risk in the meantime. Full-scale tests were carried out to study thermal smoke movement characteristics, including smoke development, longitudinal temperature distribution in the room, and horizontal temperature distribution in the ring corridor, in an indoor pedestrian street under different mechanical smoke exhaust modes. Results showed that smoke movement characteristics were mainly influenced by the smoke exhaust mode and building structure. Under natural ventilation, thermal smoke spread along the two crossed channels of the room and entered the adjacent ring corridor and atrium. When the smoke exhaust system was activated, the smoke spread was effectively restricted. As the smoke exhaust was enhanced, the heat release rate of the ventilation controlled fire in the room was increased, resulting in the higher smoke temperature. In addition, the smoke temperature rise decreased exponentially with the increasing longitudinal distance from the fire in the room under all smoke exhaust modes. The stronger smoke exhaust and larger building space leaded to the higher decay rate. In the ring corridor, the decrease of smoke temperature rise with the horizontal distance was exponential under natural ventilation but was linear when the smoke exhaust system was activated. • Thermal smoke spread characteristics in indoor pedestrian street investigated. • Room fire scenarios under four mechanical smoke exhaust modes designed. • Smoke development and temperature distribution in room and ring corridor analyzed. • Effect of different mechanical smoke exhaust modes on smoke spread revealed. • Dimensionless exponential and linear smoke temperature decay models established.

Evaluation of Children's Thermal Environment in Nursery School: Through the Questionnaire and Measurement of Wearable Sensors Approach.

Due to psychological and physical differences, children are more vulnerable to the influence of the surrounding environment than adults. A nursery school in Japan was selected as the research object. The actual thermal environment of children aged 1 to 5 in the classroom was evaluated based on measured data in winter and summer. Through a questionnaire survey of nursery teachers, this paper analyzed and compared the relationship between teachers’ thermal adaptation behavior and children’s thermal sensation. Compared with the traditional fixed-points measurement method, a method of wearable sensors for children was proposed to measure the indoor temperature distribution. The traditional measurement results showed that 73% of classroom indoor temperatures and humidity do not meet the thermal comfort standard stipulated by the government. The method proposed in this paper indicates that: (1) nursery teachers’ thermal adaptation behavior may not be based on children’s thermal sensations; (2) solar radiation and weather context could lead to uneven indoor horizontal temperature distribution, hence, specific attention should be paid to the thermal environment when children move to the window side; and (3) the density of occupants causes the temperature around the human body to be relatively high. We suggest that teachers improve the thermal comfort of gathered children through thermal adaptive behaviors. The results of the study provide valuable information for nursery managers to formulate effective indoor thermal environment strategies from the perspective of children.

Effect of the roadside tree canopy structure and the surrounding on the daytime urban air temperature in summer

As an important component of urban forests, roadside trees provide cooling and humidification effects, thereby improving the microclimate and human thermal comfort during hot summer weather by blocking, reflecting and absorbing solar radiation. However, the complex three-dimensional (3D) structure of roadside trees, diverse planting types and complex landscape heterogeneity complicate efforts to quantify the effects of these factors on above-road air temperatures. In this study, a terrestrial laser scanner (TLS) is used to accurately estimate roadside tree morphological parameters, such as the tree height (TH) and the diameter at breast height (DBH), and canopy structural parameters, such as the canopy thickness (CT), the canopy cover above the road (CCAD), canopy volume over the road (CVAD) and the leaf area index (LAI), to evaluate different 3D canopy geometries (pyramidal, spherical, pileate and cylindrical). A moving meteorological station was used to continuously obtain the horizontal air temperature (AT) distribution to investigate the effects of the canopy structural parameters, the planting types and the land cover types on the above-road AT. The value of ΔAT was positively correlated with TH, CVAD, LAI and CCAD. These structural variables were most significantly correlated with ΔAT under the pileate canopy shape. However, there were no significant correlations between these factors under the cylindrical canopy shape. The physiological equivalent temperature (ΔPET) reached 7.4, 15.8, 4.5 and 17 °C under the cylindrical, spherical, pyramidal and pileate shapes, respectively. The ΔAT of a two-sided planting was approximately 1.7 times greater than that of a one-sided planting; the ΔRH showed a similar trend. Within 230 m of a lake, the ΔAT exhibited a logarithmic relationship with the distance from a given point to the lake. Our study quantifies the influence of the roadside tree structure on the thermal environment, which can serve as a meaningful reference for urban tree species selection and arrangement.

An assessment of radiative impacts of CO2 on baroclinic instability using idealized life cycles

AbstractInteraction between CO2 and atmospheric radiation has a significant part in changing horizontal and vertical temperature distributions, through which it can affect the midlatitude atmospheric dynamics. Baroclinic instability, which is the energy source of large‐scale eddy formation in midlatitudes, depends on meridional and vertical eddy fluxes of heat. While several studies have been devoted to the impact of CO2 concentration present in the atmosphere on baroclinic eddies in climate time‐scales, the current work aims to determine the corresponding impact over a period of 10 to 20 days relevant to the duration of baroclinic life cycles when the flow is deterministically predictable. To this end, the radiative parametrization scheme called RRTMG (Rapid Radiative Transfer Model for General Circulation Models) has been coupled with the Diabatic Contour‐Advective Semi‐Lagrangian (DCASL) dynamical core. Except for parametrization of radiation as well as surface processes to represent radiative interaction with the surface, no other physics parametrizations are included in the model. The idealized life‐cycle experiments are carried out for both the predominantly anticyclonic (LC1) and cyclonic (LC2) Rossby wave breaking with the same initialization but five different CO2 concentrations (0, 250, 500, 750 and 1,000 ppmv). The impacts of different CO2 concentrations on eddy growth, mean flow and eddy–mean flow interaction are discussed. Results show that the presence of CO2 has a damping effect on instability in the baroclinic growth stage, amounting to about 7% and 4% reduction in the peak value of domain area‐average eddy kinetic energy for LC1 and LC2, respectively. In addition, increase in CO2 concentration has a small negative impact on the growth rate, vertical eddy propagation and jet intensification.

Natural convection induced by unintended horizontal temperature distribution in a narrow-closed container heated from above

This study aims at expressing the velocity fields of the liquids held in a narrow-closed container heated from above as a function of the dimensions of the container to estimate the diffusion-dominant condition. The motions of tracer particles in liquid salol held in a quasi-two-dimensional glass cell were tracked in cavities of various inner width W through the series of experiments. The mean velocity of the tracer particles, Vmean, decreased almost linearly with the decrease in the values of W. Thermal flow fields were successfully reproduced by the series of numerical simulations. We found that the unintended horizontal temperature difference is realized, which induces the natural convection in the closed narrow cavity heated from above. We derived the correlation between the Reynolds and Grashof numbers, which are described as a function of the mean velocity and the unintended horizontal temperature difference, respectively. The threshold of the convection onset in the present geometry was then proposed.

Thermal Tides in the Upper Cloud Layer of Venus as Deduced From the Emission Angle Dependence of the Brightness Temperature by Akatsuki/LIR

AbstractThe brightness temperature of the Venus disk obtained by Longwave Infrared Camera (LIR) on board Akatsuki shows clear limb darkening at low and middle latitudes. The profile of limb brightness reflects the vertical distributions of atmospheric temperature and the optical thickness of the cloud particles. Horizontal distributions of brightness temperature obtained by LIR during ∼5.8 Venusian years were analyzed to investigate the vertical structure of the brightness temperature distribution above the cloud tops based on the emission angle dependence of the sensing altitude. Emission angles were converted to sensing altitudes by a radiative transfer calculation with nominal temperature and cloud particle distributions based on past observations. We show a local time‐altitude cross section of the brightness temperature deviation above the cloud tops for three latitudinal zones. The derived vertical amplitude distribution of the diurnal and semidiurnal tides above ∼68 km is mostly explained by the classical theory of thermal tides. A semidiurnal tide in which the phase shifts upstream with altitude is clearly seen in the equatorial region. By applying the dispersion relation of the internal gravity wave to the observed wave structure, it was found that the zonally averaged zonal wind velocity at altitudes of 66–71 km was approximately the same as the known superrotation velocity. By comparing the observed and simulated vertical phase structures, it is suggested that the tidal wave structure seen in the equatorial cloud tops is an aspect of upward propagation of a gravity wave generated in the upper cloud layer by solar heating.

Numerical Study of the Thermal Structure and Circulation in a Large and Deep Dimictic Lake Over Tibetan Plateau

AbstractA three‐dimensional (3‐D) hydrodynamic model based on the Princeton Ocean Model (POM) was applied to simulate the thermal structure and circulation of Lake Nam Co (LNC), the third largest lake over the Tibetan Plateau (TP), during May–December 2013. Compared with a spatially distributed set of one‐dimensional thermal diffusion lake models, POM better reproduced the observed seasonal evolution of the horizontal distribution of lake surface temperature and the vertical thermal structure. A heat budget analysis confirmed that the lateral heat exchange made significant contributions to the horizontal variability of lake temperature. The model results showed that LNC was thermally stratified in summer, had a weak inverse stratification since mid‐December, and was fully turned over during late spring and autumn. During both overturning phases, the modeled “thermal bar” was developed as a result of the density‐driven convection in response to the radiative heating (surface cooling) during spring (autumn). The 3‐D model results showed that the monthly mean circulation featured a predominant mid‐lake cyclonic gyre throughout the ice‐free period; upwelling along the western coast and strong coastal currents occurred in all months except in July–August. Model sensitivity experiments confirmed that the lake circulation was primarily driven by the barotropic dynamics of the prevailing southwesterly wind, while the baroclinic process made a secondary contribution. The results pointed out the necessity to resolve lateral processes when modeling large TP lakes.

A new assessment of the circulation of Atlantic and Intermediate Waters in the Eastern Mediterranean

A simulation of the Mediterranean circulation between 2011 and 2020 at a resolution of 3–4 km in the Eastern basin was compared to vertical profiles and horizontal distributions of temperature and salinity from Argo profilers distributed throughout the basin. The comparison is marked by high temporal (∼0.9) and spatial (0.6–0.8) correlations and low biases. Comparisons of SST with satellite imagery have also shown strong similarities for numerous structures over a wide range of spatial scales. The simulation is used to describe the mean circulation of surface Atlantic Waters and Intermediate Waters in winter and summer.The surface circulation is cyclonic alongslope, stronger and more stable in winter. In summer, the current veins are sometimes interrupted and replaced by trains of eddies like in the South Ionian. In other cases, the current becomes very narrow and stuck to the coast as along the Ionian east coast or the Middle East coast. In winter, surface and Levantine Intermediate Waters exit from the Levantine mainly through the Aegean, while in summer, they exit westward south of Crete. The Aegean tends in summer to be isolated by eddies that develop on both sides of the Cretan Arc. The juxtaposition of Ierapetra, the Rhodes Gyre and the Mersa-Matruh Eddies produces a southward path across the Levantine basin at about 27 − 28°E which delimits a large cyclonic circulation to the east which tends to separate the two parts of the basin (west and east Levantine). Concerning the Levantine Intermediate Waters, the alongslope cyclonic circulation all around the Levantine basin in winter is no longer maintained in summer as a large anticyclonic circulation occupies the southeast of the basin. The intermediate waters entering the Ionian either through southern Crete in summer or through the Aegean in winter, are submitted to a strong northward, southward and even westward dispersion by Pelops and the nearby anticyclonic areas. The presence of recurrent anticyclones between 35 and 37°N along a band extending from west to east of the Ionian also produces a vertical dispersion of intermediate water. Finally, the circulation of intermediate water in the South Ionian is marked by an important seasonality with the presence in summer of a large anticyclonic circulation that seems to be wind induced and finally drives a secondary branch to the Sicily Channel. A climatology for the transport through the different straits is discussed and simplified representations of the circulation are proposed.

A novel interconnect design for thermal management of a commercial-scale planar solid oxide fuel cell stack

Solid oxide fuel cell (SOFC) is a promising technology for stable power supply with high efficiency and high quality heat utilization, but it still faces the technical challenge of low long-term durability caused by thermal imbalance of its stack. An effective, novel thermal management method is urgently required for its market deployment. This study proposes a novel interconnect design for effective thermal management and elucidates the influence of its design variables on internal thermal conditions and heat transfer characteristics of a 1-kW planar SOFC stack. Three-dimensional thermo-fluid simulations are performed on the new stack design employing the novel interconnect and the conventional stack design for comparison. The new design is developed for the purpose of uniform in-plane (horizontal) temperature distribution by modifying the displacement of gas manifolds. At the repeating-unit scale, due to the reduced thermal resistance for horizontal heat transfer of the new stack, its in-plane temperature deviation decreases by 35–60 °C. At the stack scale with 30 unit-cells stacked vertically, the average temperature increases by 30 °C, and the vertical temperature difference decreases by 50 °C. Such thermal fields are the combined results of reduced gaseous convection and enhanced vertical solid-phase conduction through each repeating unit. In the new stack, the amount of heat transferred to the gas within each repeating unit is generally decreased, but is recuperated by increasing solid conduction through metallic interconnects. The relatively weakened gaseous heat transfer of the new design provides more thermal load at the lowest unit of the stack than the reference design, which promotes gas pre-heating prior to reaching the unit-cells and hence results in the elevated stack temperature. Such gas pre-heating also reduces the temperature difference in the vertical direction of the new design. The lower temperature differences both in horizontal and vertical directions enable the new stack to reduce its thermal imbalance and potentially to improve long-term durability.

Numerical analysis of horizontal temperature distribution in large buildings by thermo-aeraulic zonal approach

Numerical analysis of horizontal temperature distribution in large buildings by thermo-aeraulic zonal approach

Experimental Study on the Inverse Estimation of Horizontal Air Temperature Distribution in Built Spaces Using a Ground-Based Thermal Infrared Spectroradiometer

Air temperature is an important physical indicator for urban and architectural environments; however, it is difficult to obtain its distributive characteristics by field measurements owing to the limitations of current measuring instruments. In this context, this study was conducted to demonstrate whether a small and portable ground-based thermal infrared spectroradiometer can be used to estimate the horizontal air temperature distribution in built spaces. For this estimation, we first calculated a forward model using radiative transfer simulations, and the air temperature distribution was inversely estimated from the observed radiance using the model. To regularize the estimated air temperature, we used the maximum a posteriori method, which uses prior information. To verify this estimation method, we conducted measurement experiments in two types of built spaces that had different air temperature distributions within spaces that were approximately 20 m long. Moreover, we conducted a parametric case study on the prior information. As a result, we were able to estimate the air temperature distribution with an average root mean square error (RMSE) of 1.3 °C for all cases when the average RMSE of the prior information for all cases was 2.1 °C. This improvement in the RMSE indicates that this method is able to remotely estimate the horizontal air temperature distribution in built spaces.

TDC-based horizontal leakage area estimation in multiunit residential buildings: Three correction factors

Infiltration and interzonal airflow driven by wind and stack interactions in a multi-unit residential building (MURB) are crucial factors affecting indoor air and environmental qualities. To analyze the weather-driven airflow in MURBs, it is essential to define accurately the horizontal leakage areas for serial airflow paths on typical and basement floors in the multizone airflow modeling. Considering the challenges in measuring numerous leakage areas, a horizontal leakage estimation method based on the thermal draft coefficient (TDC) is proposed, in which the leakage areas are calculated by the stack-driven pressure differences relatively easy to measure. Moreover, three correction coefficients are theoretically suggested to minimize the TDC uncertainties from (1) different household envelope areas, (2) horizontal temperature distributions on each floor, and (3) multiple shafts in real MURBs. Two validation studies were conducted in a real MURB. First, the TDC-based models were validated by CONTAMW, and the effectiveness of the three correction factors was shown in the simulation-based case. The envelope area ratio correction factor was most effective for leakage areas in dwelling units. The shaft ratio correction factor was necessary for elevator doors on typical floors and all leakage areas on basement floors. The air density correction factor could improve all leakage areas under the horizontal temperature distributions on each floor. Then, based on field measurements, the proposed method was applied to leakage estimation in the building. Compared with the existing method, the field-measurement-based validation case demonstrated a significant improvement in the leakage estimation under measurement uncertainties.

Distributed fiber optic measurements of strain and temperature in long-span composite floor beams with simple shear connections subject to compartment fires

This study explores an instrumentation strategy using distributed fiber optic sensors to measure strain and temperature through the concrete volume in large-scale structures. Single-mode optical fibers were deployed in three 12.8 m long steel and concrete composite floor specimens tested under mechanical or combined mechanical and fire loading. The concrete slab in each specimen was instrumented with five strain and temperature fiber optic sensors along the centerline of the slab to determine the variation of the measurands through the depth of the concrete. Two additional fiber optic temperature sensors were arranged in a zigzag pattern at mid-depth in the concrete to map the horizontal spatial temperature distribution across each slab. Pulse pre-pump Brillouin optical time domain analysis (PPP-BOTDA) was used to determine strains and temperatures at thousands of locations at time intervals of a few minutes. Comparisons with co-located strain gauges and theoretical calculations indicate good agreement in overall spatial distribution along the length of the beam tested at ambient temperature, while the fiber optic sensors additionally capture strain fluctuations associated with local geometric variations in the specimen. Strain measurements with the distributed fiber optic sensors at elevated temperatures were unsuccessful. Comparisons with co-located thermocouples show that while the increased spatial resolution provides new insights about temperature phenomena, challenges for local temperature measurements were encountered during this first attempt at application to large-scale specimens.

Measurements and Analysis of Thermal Environment of University Class Room for Optimal Control of Air Conditioning Equipment in Large Space

The authors conducted in the previous study that numerical experiments to inversely estimate the optimal air conditioning outlet temperature according to the target temperature. Numerical experiments showed the usefulness of the air conditioner control method using the SR method. However, when applying the SR method in real space, the accuracy of the SR method depends on the accuracy of CFD calculation. Therefore, in this study, as a preliminary step to the application of the SR method to the real space, the thermal environment of the real space was measured and compared with the CFD calculation results. Almost no horizontal temperature distribution was seen in the real space. From this result, it was found that there is a problem in creating the indoor space temperature distribution.

Numerical model to predict water temperature distribution in a paddy rice field

Irrigating water into a paddy field inevitably changes the water temperature and produces a temperature distribution in the field. In this study, a numerical model for predicting the horizontal water temperature distribution in a paddy field was developed. In addition to considering the heat exchange between the atmosphere, paddy rice, water, and soil, the model also considers the horizontal heat convection within the paddy field due to the inflow of irrigation water and outflow of paddy field water. The horizontal water flow in the field is modeled by the water balance equation of paddy water. The model was validated using field measurements collected in a paddy field where the continuous irrigation with running water (CIRW) management method was applied. The calculated changes in water temperatures over time and distance showed good agreement with the observed values. Further, the root mean square error (RMSE) of the water temperature during the entire validation period was 0.98 °C, and the RMSE during the nighttime CIRW irrigation was 0.55 °C. These results indicate that the model satisfactorily expresses the features of paddy water temperature distribution under the effect of irrigation water inflow. Moreover, a comparison of the calculation results of the proposed model to those of the conventional methods that do not consider the water temperature distribution demonstrated that the prediction accuracy significantly improves when the water temperature distribution is considered. Our results suggest that the prediction of water temperature distribution is useful for a more accurate prediction of paddy heat environment and various phenomena affected by water temperature in a paddy field.