Typical Summer Conditions Research Articles

Research on Design and Operation Methods of Radiant Panel with Fresh Air System

Compared with traditional air-conditioning systems which aim at maintaining the designed indoor air temperature and humidity, radiant panels are capable to improve the human thermal comfort through the direct radiant heat transfer with occupants. Based on the Fanger’s thermal comfort model, the simplified PMV (Predicted Mean Vote) model and calculation equation of cooling load are established. This paper analyzes the relationship between the human thermal comfort and indoor sensible cooling load, and explores the design and operation methods of indoor parameters. The model room with typical boundary conditions in the hot-summer and cold-winter zone of China is simulated and analyzed by Airpak. The widely accepted PMV and PPD (Predicted Percentage of Dissatisfied) indices are adopted to evaluate the indoor human thermal comfort. The parameters including the radiant surface temperature, the air supply temperature, the relative humidity and the ratio of the radiant surface areas are researched. The optimum indoor parameters in typical summer conditions are finally obtained, it is expected to provide a relevant reference for the design and operation methods subject to the radiant panel combined with fresh air system.

Optimization analysis of a hybrid fresh air handling system based on evaporative cooling and condensation dehumidification

This paper studies a fresh air handling system, which is composed of a mechanical compression refrigeration system and an evaporative cooling system. In an effort to improve the basic systems, a single-stage total heat recovery module consisting of a cooler and a spray packing is incorporated into the system (process I). The results show that when keeping the total heat and mass transfer capability constant, the coefficient of performance (COP) of process I first increases and then decreases with increasing heat and mass transfer capability of the total heat recovery module. Under typical summer conditions, the optimum COP of process I is 8.5% higher than that of the conventional system. To reduce the exergy destruction in the total heat recovery module and increase the supply air temperature, a single-stage sensible heat recovery module is also incorporated (process II), leading to a further increase in the optimum COP of 3.3% and suitable supply air temperature. A test device based on process II was constructed to experimentally validate the simulation results. The experimental results demonstrate that the system performance is better for high temperature and humidity fresh air conditions owing to the higher proportion of total heat recovery.

Laboratory assessment of residential building walls containing pipe-encapsulated phase change materials for thermal management

To reduce the heat flow between building interior and exterior environments using thermal energy storage without causing problems related to moisture transfer, this paper presents residential building walls enhanced with pipe-encapsulated phase change materials (PCM). Experimental investigations are conducted to identify thermal performance of building walls with pipe-encapsulated PCM in typical summer conditions. A dynamic wall simulator was designed and built to reproduce residential building indoor and outdoor conditions in a laboratory setting. Two pipe sizes, based on diameter, installed in a horizontal arrangement and placed at various wall depths were investigated. The heat transfer through building walls with pipe-encapsulated PCM was evaluated based on peak heat flux reductions and peak heat flux time shift. The peak heat fluxes of the PCM-outfitted walls were reduced by a maximum of 22.5% for what was referred to as “next to wallboard” configuration and 36.5% for “middle depth” configuration, respectively, compared to standard walls. The corresponding daily energy savings were 27.4 W-hr/m2 and 51.2 W-hr/m2. PCM encapsulated in smaller pipes installed in the “middle depth” of the wall cavity is recommended to realize complete solidification and melting for larger peak flux reduction and energy savings.

Forecasting carbon monoxide on a global scale for the ATom-1 aircraft mission: insights from airborne and satellite observations and modeling

Abstract. The first phase of the Atmospheric Tomography Mission (ATom-1) took place in July–August 2016 and included flights above the remote Pacific and Atlantic oceans. Sampling of atmospheric constituents during these flights is designed to provide new insights into the chemical reactivity and processes of the remote atmosphere and how these processes are affected by anthropogenic emissions. Model simulations provide a valuable tool for interpreting these measurements and understanding the origin of the observed trace gases and aerosols, so it is important to quantify model performance. Goddard Earth Observing System Model version 5 (GEOS-5) forecasts and analyses show considerable skill in predicting and simulating the CO distribution and the timing of CO enhancements observed during the ATom-1 aircraft mission. We use GEOS-5's tagged tracers for CO to assess the contribution of different emission sources to the regions sampled by ATom-1 to elucidate the dominant anthropogenic influences on different parts of the remote atmosphere. We find a dominant contribution from non-biomass-burning sources along the ATom transects except over the tropical Atlantic, where African biomass burning makes a large contribution to the CO concentration. One of the goals of ATom is to provide a chemical climatology over the oceans, so it is important to consider whether August 2016 was representative of typical boreal summer conditions. Using satellite observations of 700 hPa and column CO from the Measurement of Pollution in the Troposphere (MOPITT) instrument, 215 hPa CO from the Microwave Limb Sounder (MLS), and aerosol optical thickness from the Moderate Resolution Imaging Spectroradiometer (MODIS), we find that CO concentrations and aerosol optical thickness in August 2016 were within the observed range of the satellite observations but below the decadal median for many of the regions sampled. This suggests that the ATom-1 measurements may represent relatively clean but not exceptional conditions for lower-tropospheric CO.

Evaporation Loss During Sprinkler Irrigation

This study investigates the factors influencing evaporation loss from sprinkler systems during operation. Through analysis, it is determined that evaporation is influenced by climate demand, time of operation, and water droplet surface area. A nomograph is introduced to estimate evaporation loss, with findings suggesting an average daily loss of 1.5 percent in Gainesville, Florida. Moreover, operation during early afternoon hours in typical summer conditions may lead to a 3 percent loss. Conversely, minimal loss is expected during nighttime and early morning operations. Strategies to mitigate evaporation loss include adjusting operating conditions to increase droplet size and avoiding high climate demand periods. Conversely, factors such as using small nozzles and operating at high pressures can exacerbate evaporation loss, particularly during peak climate demand periods. It is emphasized that adherence to manufacturer-recommended pressure ranges is crucial to prevent performance issues.

Estimation of Direct Radiative Effects of Background and Smoke Aerosol in the IR Spectral Region for Siberian Summer Conditions

We present estimates of direct radiative effects (DRE) for background and smoke aerosol in the IR spectral region. The estimates are obtained using an original Monte Carlo algorithm and OPAC models for typical summer conditions and smoke haze conditions on the territory of Siberia in 2012. It is shown that the DRE value at the atmospheric boundaries in the thermal spectral region is approximately 3% of the daily mean radiation effect in the solar spectral region under background conditions, and 10–15% under conditions of strong turbidity.

Evaluation on the Performance of Photovoltaic–Thermal Hybrid System Using CO2 as a Working Fluid

In this study, the CO2-based photovoltaic–thermal hybrid system has been investigated with an objective to increase the power generation efficiency in photovoltaic solar panel and to improve the performance of supercritical CO2 solar Rankine cycle system (SRCS). From a previous study, an improvement of 2% of power generation efficiency was confirmed via experimental investigation. In this study, the temperature distribution on the CO2-based photovoltaic–thermal hybrid system has been numerically and experimentally investigated and confirmed with referenced experimental results. Particularly, in this study, the one-dimensional (1D) calculation of CO2 flow in the cooling tube and three-dimensional (3D) calculation of temperature distribution on the surface of the photovoltaic solar panel are conducted. The typical summer and winter weather conditions are used as the calculation references to investigate the effect of temperature distribution of the photovoltaic solar panel. The results show that the trend of temperature distribution from calculation was confirmed with the experimental data both in summer and winter conditions. Furthermore, in summer condition, the CO2 temperature was increased to a maximum of 28 °C.

High-frequency productivity estimates for a lake from free-water CO<sub>2</sub> concentration measurements

Abstract. Lakes are important actors in biogeochemical cycles and a powerful natural source of CO2. However, they are not yet fully integrated in carbon global budgets, and the carbon cycle in the water is still poorly understood. In freshwater ecosystems, productivity studies have usually been carried out with traditional methods (bottle incubations, 14C technique), which are imprecise and have a poor temporal resolution. Consequently, our ability to quantify and predict the net ecosystem productivity (NEP) is limited: the estimates are prone to errors and the NEP cannot be parameterised from environmental variables. Here we expand the testing of a free-water method based on the direct measurement of the CO2 concentration in the water. The approach was first proposed in 2008, but was tested on a very short data set (3 days) under specific conditions (autumn turnover); despite showing promising results, this method has been neglected by the scientific community. We tested the method under different conditions (summer stratification, typical summer conditions for boreal dark-water lakes) and on a much longer data set (40 days), and quantitatively validated it comparing our data and productivity models. We were able to evaluate the NEP with a high temporal resolution (minutes) and found a very good agreement (R2≥0.71) with the models. We also estimated the parameters of the productivity–irradiance (PI) curves that allow the calculation of the NEP from irradiance and water temperature. Overall, our work shows that the approach is suitable for productivity studies under a wider range of conditions, and is an important step towards developing this method so that it becomes more widely used.

Study on performance of a novel energy-efficient heat pump system using liquid desiccant

In this paper, a novel heat pump system is proposed, which operates as a heat-source-tower heat pump with no frosting in winter, and as a hybrid refrigerant system consisting of a conventional chiller combined with a liquid desiccant dehumidification and evaporative cooling subsystem in summer. A validated mathematical model of the proposed system operating in summer is established to investigate the effects of key parameters, including solution to refrigerant flow ratio (FR), condensation heat recovery ratio (Rcond) and ambient parameters, on the cooling performance. Besides, this paper analyzes key factors that should be considered in designing the heat exchange area of the solution-cooled condenser (SCC). The results show that the maximum COP and ECOP of the heat pump system are 13.4% and 10.3% higher than those of conventional vapor compression refrigerant systems under the typical summer condition of Nanjing, respectively. The recommended range of FR is from 1.2 to 6 and that for Rcond is from 16% to 40%. Moreover, the proposed system is more superior to conventional ones when applied in hot and humid regions.

Kinematic parameters of internal waves of the second mode in the South China Sea

Abstract. Spatial distributions of the main properties of the mode function and kinematic and non-linear parameters of internal waves of the second mode are derived for the South China Sea for typical summer conditions in July. The calculations are based on the Generalized Digital Environmental Model (GDEM) climatology of hydrological variables, from which the local stratification is evaluated. The focus is on the phase speed of long internal waves and the coefficients at the dispersive, quadratic and cubic terms of the weakly non-linear Gardner model. Spatial distributions of these parameters, except for the coefficient at the cubic term, are qualitatively similar for waves of both modes. The dispersive term of Gardner's equation and phase speed for internal waves of the second mode are about a quarter and half, respectively, of those for waves of the first mode. Similarly to the waves of the first mode, the coefficients at the quadratic and cubic terms of Gardner's equation are practically independent of water depth. In contrast to the waves of the first mode, for waves of the second mode the quadratic term is mostly negative. The results can serve as a basis for expressing estimates of the expected parameters of internal waves for the South China Sea.

Thermal comfort and energy performance of public rental housing under typical and near-extreme weather conditions in Hong Kong

Building performance evaluation is crucial for sustainable urban developments. In high-density cities, occupants suffer from poor living conditions due to building overheating, especially during increasingly frequent near-extreme summer conditions caused by climate change. To represent this situation, the summer reference year weather data was employed for building simulations using DesignBuilder. This study aims to evaluate the thermal comfort and energy consumption of four typical public rental housing (PRH) building types in Hong Kong. For free-running flats, results show generally higher air temperatures in the oldest PRH type (Slab) with a compact linear building form and the most sensitive response to outdoor temperature changes for another older PRH type (Trident) with a Y-shaped design, possibly owing to its high wall conductivity. Occupants in all building types experience a ∼10% increase in the proportion of discomfort hours when compared to results for typical summer conditions, but overheating is the most severe in Slab type PRH. Following an initial assessment of the cooling energy usage, a simple sensitivity test was conducted to explore the potential energy savings by various passive design strategies, including shading and reducing the exposed cooled space. A cross-shaped building form also appears to be more energy efficient. These findings, complemented by further parametric analyses, may prove useful when designing buildings for climate change.

Intercomparison of boundary layer parameterizations for summer conditions in the eastern Mediterranean island of Cyprus using the WRF - ARW model

Ten planetary boundary-layer (PBL) parameterization schemes in the Weather Research and Forecasting (WRF) model have been evaluated with respect to temperature and wind forecasts for typical summer conditions in the eastern Mediterranean island of Cyprus. An ensemble of twenty-two simulations was performed, for a combination of the ten PBL and compatible surface layer parameterization schemes and each of the setups has been evaluated in view of forecasting skill and other statistical indices. Comparison of the model results with measurements from eight sites in Cyprus revealed significant differences in forecast skill, during both daytime (unstable conditions) and nighttime (stable conditions). The time series produced by the simulations were assessed against observations, in an effort to identify biases and skills in the forecasting ability of the models, employing commonly used statistical performance measures, such as the Mean Error, Mean Absolute Error, Mean Squared Error and Root Mean Squared Error. In summary, most simulations exhibit a negative bias for all stations concerning temperature and nearly all have positive biases for wind speed and direction. Statistical analysis of the results identified the best performing parameterization configurations for further investigation, to determine the most suitable setup for summertime forecasting in Cyprus, focusing on coastal stations, where land – sea breeze circulations govern the diurnal weather characteristics.

Numerical and experimental study of a passive solar still integrated with an external condenser

This paper presents a numerical and experimental investigation to study the effect of the condenser area on the Natural Circulation Loop (NCL) solar still features under typical summer and winter conditions. A computer code has been developed to predict the transient thermal behaviour of the still. This computer code is used to predict the effect of condenser area and wind velocity, on the still daily yield in summer and winter conditions. The results revealed that the still daily productivity increases with the increase of the condenser area until a critical value beyond which its effect becomes insignificant. In addition, it was found that the wind effect is more effective for small condenser area. The simulation shows that the maximum daily output of NCL solar still, under summer and winter conditions, can reach 4.73 kg/m2 and 2.71 kg/m2, respectively.

Investigation of heat transfer and temperature distribution in outdoor human–clothing–environment systems with double-layered ensemble

The thermal behavior in a clothing microclimate is an important aspect related to thermal comfort. Situation-dependent analyses are required to understand the heat transfer of clothing; thus, the heat transfer and temperature distributions in a double-layered human–clothing–environment system in the presence of solar radiation are investigated as practical application in this study. A new heat transfer model modified from the previously proposed outdoor thermal model with single-layered clothing is developed. The new model integrates the radiative effects on clothing, the heat conduction within the air layer, and the heat convection on the outer surface of clothing. Radiation heat transfer is included as a source term for the clothing. Measurements of the temperature distributions are obtained under typical summer and winter atmospheric conditions with or without solar radiation to validate the model. A comparison confirms that the prediction model is valid. Subsequently, the effects of layered clothing are analyzed. Since insulation fundamentally influences the temperature distributions in the steady-state system, the temperatures at the boundary and air gap determine the slopes of the temperature distribution. Since the absorbed solar energy is more influential than the release of heat by conduction or even convection for clothing, the solar radiation and radiative properties are relatively dominant at the temperature distribution of clothing and consequently the entire system. Overall, the effects of solar radiation and the properties related to radiation are essential for evaluating the microclimate inside clothing.

Particle dynamics of the surface, intermediate, and benthic nepheloid layers under contrasting conditions of summer monsoon and typhoon winds on the boundary between the Taiwan Strait and East China Sea

Two shipboard surveys of hydrographics and sediment dynamics were conducted off the mouth of Minjiang (the Min River) in July 2012, under contrasting summer monsoon and typhoon wind conditions. Observations included profiles of conductivity, temperature, depth, fluorescence, and suspended-particle volume concentration and current velocity. In addition, water samples were taken for the analyses of mass concentration, POC, and chlorophyll of suspended sediment. Seafloor sediment samples were also taken for grain-size analysis. Nepheloid layers (NLs) were observed at surface, intermediate, and benthic depths (SNL, INL, BNL, respectively). The NL dynamics under the two wind conditions were mainly controlled by (1) the presence of the Minjiang river plume and terrigenous material it carries; (2) water-column stability affected by wind, current, and waves; (3) current-induced resuspension of seafloor sediment; and (4) physically coupled biological activities. The wind field was the major forcing controlling the observed flow field and the upper water column stability. In the typical summer condition, southerly winds induced offshore-directed currents, enhancing the seaward dispersal of the Minjiang river plume, facilitating water-column stratification, thereby forming 3 NLs in the water column. Phytoplankton growth was enhanced by terrigenous material and sunlight. The suspension of the seafloor sediment was the one of the major sources for suspended particles in these NLs. Furthermore, the C/N ratio of POC in the three NLs is 5.72, almost identical to the Redfield ratio, indicating their predominant marine origin. Conversely, under typhoon-related northerly winds, the offshore spread of the river plume was restricted. The reduced riverine input and enhanced mixing resulted in the disappearance of the SNL. Elevated turbidity in the INL was largely due to the presence of phytoplankton, while the BNL was comprised of sediment resuspended off the seafloor and from horizontal advection. Our results suggest that the presence of the river plume from the Minjiang at the study site sets the condition for the SNL dynamics. The dynamics of INL and BNL were dominated by the wind field, and to a lesser degree, the wave field and tidal current.

Performance assessment of a single/double hybrid effect absorption cooling system driven by linear Fresnel solar collectors with latent thermal storage

Coupling with a single/double hybrid effect (SDHE) absorption system could cut down the investment cost and increase significantly the average coefficient of performance. A hybrid solar hybrid cooling system, composed of linear Fresnel reflector (LFR) solar collector arrays, a single/double hybrid effect (SDHE) absorption chiller, a thermal storage tank stored the intermediate-temperature HITEC molten salt, and complementary components, was investigated both theoretically and experimentally in this paper. Based on the weather data of typical meteorological year, dynamic mathematical models coupled with different operation modes have been developed and were validated with the experimental results of each component. The objective of this paper is to theoretically analyze the complicated dynamic behaviors of LFR solar collector, SDHE absorption chiller, and the entire solar cooling system. Experimental results show the SDHE absorption chiller can obtain thermal COP from 0.73 (single effect) to 1.09 (double effect) when the inlet temperature of hot water increased from 141.5°C to 155.4°C. Considering the same weight coefficient of cooling capacity, solar fraction, and thermal COP on seasonal performance, the optimized region of collecting area and thermal storage capacity are within the ranges of 900–1100m2 and 5–8.5m3, respectively. The optimized concentration ratio of 30 is determined based on the second law of thermodynamics and the rated parameters of the SDHE chiller. Finally, the optimized solar cooling system can provide the average seasonal cooling capacity of 102kW, the seasonal thermal COP of 0.88, and the seasonal solar fraction of 27.2% in typical meteorological summer conditions of Shanghai.

CTCP temperature fields and stresses

Cross-tensioned concrete pavements (CTCPs) are used in the construction of continuous Portland cement concrete pavements. They eliminate the need for transverse joints and also restrict cracking of the pavement. A CTCP consists of three components, namely, the CTCP slab, the sand sliding layer (SSL), and the cement-stabilized macadam base, from top to down. The retard-bonded tendons (RBTs) of the CTCP slab are arranged diagonally. In the present study, a detailed 3D finite element model was developed and used to examine the temperature fields and stresses of a CTCP by thermal-mechanical coupling analysis, and the results were compared with field measurements. The model investigations revealed that, under typical cloudless summer conditions, the temperature field of the CTCP varied nonlinearly with both time and depth. The resultant step-type temperature gradient of the CTCP represents a significant deviation from that of a conventional pavement and impacts the thermal contact resistance of the SSL. It was found that the SSL could effectively reduce the temperature stresses in the CTCP, and that the residual temperature stresses were effectively resisted by the staged cross-tensioned RBTs. The potential problem areas in the vicinity of the temperature stresses were also investigated by the finite element method and field tests.

Effects of Mixing and Curing Temperature on the Strength Development and Pore Structure of Fly Ash Blended Mass Concrete

The aim of this work is to know clearly the effects of temperature in response to curing condition, hydration heat, and outside weather conditions on the strength development of high-performance concrete. The concrete walls were designed using three different sizes and three different types of concrete. The experiments were conducted under typical summer and winter weather conditions. Temperature histories at different locations in the walls were recorded and the strength developments of concrete at those locations were measured. The main factors investigated that influence the strength developments of the obtained samples were the bound water contents, the hydration products, and the pore structure. Testing results indicated that the elevated summer temperatures did not affect the early-age strength gain of concrete made using ordinary Portland cement. Strength development was significantly increased at early ages in concrete made using belite-rich Portland cement or with the addition of fly ash. The elevated temperatures resulted in a long-term strength loss in both belite-rich and fly ash containing concrete. The long-term strength loss was caused by a reduction in the degree of hydration and an increase in the total porosity and amount of smaller pores in the material.

Controls on the transport of oceanic heat to Kangerdlugssuaq Glacier, East Greenland

ABSTRACTGreenland's marine-terminating glaciers may be sensitive to oceanic heat, but the fjord processes controlling delivery of this heat to glacier termini remain poorly constrained. Here we use a three-dimensional numerical model of Kangerdlugssuaq Fjord, East Greenland, to examine controls on fjord/shelf exchange. We find that shelf-forced intermediary circulation can replace up to ~25% of the fjord volume with shelf waters within 10 d, while buoyancy-driven circulation (forced by subglacial runoff from marine-terminating glaciers) exchanges ~10% of the fjord volume over a 10 d period under typical summer conditions. However, while the intermediary circulation generates higher exchange rates between the fjord and shelf, the buoyancy-driven circulation is consistent over time hence more efficient at transporting water along the full length of the fjord. We thus find that buoyancy-driven circulation is the primary conveyor of oceanic heat to glaciers during the melt season. Intermediary circulation will however dominate during winter unless there is sufficient input of fresh water from subglacial melting. Our findings suggest that increasing shelf water temperatures and stronger buoyancy-driven circulation caused the heat available for melting at Kangerdlugssuaq Glacier to increase by ~50% between 1993–2001 and 2002–11, broadly coincident with the onset of rapid retreat at this glacier.

FEM thermal performance analysis of multi-layer external walls during typical summer conditions considering high intensity passive cooling

Quality of indoor environment as well as energy consumption in buildings are a growing concern in the context of overheating of buildings, as the EU legislation is primarily focused on heating season. The statistical data of EU have shown that there is already a large amount of buildings not comfortably cool during summer and the trend is increasing. Therefore, the main goal of this paper is to evaluate the influence of high intensity passive cooling as one of the passive solutions for overheating of buildings on the overall thermal response of building envelope systems. Specifically, a variety of multi-layer external walls during realistic summer time conditions of Central European climate were considered. For this purpose, a finite element method was used to simulate the non-stationary thermal response of several heavy weight and light weight external wall constructions. The results have shown that indoor air change intensity as well as internal heat gains have a significant impact on heat flow through the building envelope. Clear difference in thermal behaviour was detected between light weight and heavy weight envelope systems, as a consequence of different thermal mass and thermal insulation position. While the results of the conducted study represent guidelines to architects, designers, investors and other stakeholders in building industry, the growing popularity of light weight constructions, especially in residential buildings, dictates further research of building envelope configurations and passive cooling system impact on the thermal response of constructions.