Insulation Configurations Research Articles

Heat transfer finite element model of fresh fruit salad insulating packages in non-refrigerated conditions

The quality of many foods is significantly affected by temperature fluctuations that can occur during distribution and transport. Packaging materials can help to shield the product from temperature variation by increasing the heat transfer resistance. Thermal insulation power is influenced by several factors, such as material, geometry, and degree of contact between materials. To maintain the cool chain of fruit salad with syrup during the transportation (temperature less than 5 °C), thermal insulation effect of different packaging materials was investigated. A parametric analysis using a finite element model able to describe the heat transfer inside the containers, on varying packaging material (expanded polystyrene: EPS, and air), geometry, dimension, and boundary conditions, was developed and validated. Good agreement was obtained between numerical and experimental results (R2 up to 0.98). The effectiveness of the insulation configurations was evaluated by determining the time taken for the temperature to rise the critical value of 5 °C. Results showed that insulating performance of the air is better than EPS. This is realistic only taking into account insulation layer less than 0.013 m. From a practical point of view, an EPS packaging could result stronger compared to a packaging characterised by an insulating air layer. For the same EPS insulation thickness, product temperature exponentially decreases with the volumetric capacity (R2 = 0.99).

Study on Insulator Flashover Voltage Gradient Correction Considering Soluble Pollution Constituents

Natural polluted insulator surfaces are always coated with various kinds of soluble constituents, and those constituents affect flashover performance differentially. Currently, this fact is not considered either in laboratory experiments or field pollution degree measurements, causing the existing insulation selection method to be deficient. In this paper, a systematic study on insulator flashover voltage gradient correction involving different types of soluble pollution constituents is presented. Using a typical type glass insulator as the sample, its flashover tests, polluted by typical soluble chemicals (NaCl, NaNO3, KNO3, NH4NO3, MgSO4, Ca(NO3)2 and CaSO4), were carried out. Then, the flashover gradient correction was made by combining the flashover performance of each soluble constituent, the equivalent salt deposit density (ESDD) contribution of the seven constituents, and the saturation performance of CaSO4. The correction agreed with the flashover test results of insulator polluted by three types of soluble mixture. Research results indicate that the flashover gradient correction method proposed in this paper performs well in reducing the calculating error. It is recommended to carry out component measurements and flashover gradient correction to better select outdoor insulation configuration.

Three-dimensional accuracy with two-dimensional computation speed: using the Kiva™ numerical framework to improve foundation heat transfer calculations

Calculation of heat transfer from building foundations is a computationally intensive three-dimensional problem that can require several weeks to solve using current computing hardware. The Kiva numerical framework was developed to compare foundation heat transfer calculation methods and determine approaches that reduce computation time without sacrificing a balance of capability, ease-of-use, and accuracy. This paper demonstrates the application of the Kiva framework to determine an accurate method of approximating three-dimensional heat transfer effects using two-dimensional coordinate systems. In two-dimensions, problems that would otherwise take days or weeks to solve can be solved in less than a minute. Three existing two-dimensional approximation methods along with a new boundary layer adjustment method are tested across a range of foundation types, shapes, and insulation configurations. The boundary layer adjustment method is shown to provide results within 3% mean absolute deviation from the three-dimensional solution.

AC flashover performance of various types of insulators under fan-shaped non-uniform pollution

Previous simulation and observations showed that, the air flow field at windward and leeward side of insulator string will probably be different if the wind velocity is over a certain value, and thus causing the imparity of contamination degree at the two sides. In this paper, fan-shaped non-uniform polluting method was used to artificially simulate the different pollution severity at windward and leeward side of insulator string. Then, the effects of fan-shaped non-uniform pollution on ac flashover performance of 5 types of insulators were discussed. Test results indicate that, SDD, the ratio SDD of windward to leeward side (W/L), the occupation ratio of leeward side (k), will affect the ac flashover performance of insulator string. U 50 and SDD still can be expressed by the negative power function. A reduction in W/L from 1/1 to 1/15 would give a decrease about 23% in a value, which causes U 50 reducing about 25%, but n value changes little. The correction method proposed by EPRI is also applicable for fan-shaped non-uniform pollution, but has difference. A larger creepage distance of insulator does not mean that the creepage distance utilization rate is higher. Due to the influence of fan-shaped non-uniform pollution, the existing insulation configuration of transmission lines in heavily polluted areas may not satisfy the required insulation margin. The results have certain reference significance for the design and selection of transmission line external insulation.

Analysis and Parametric Study of Partially Composite Precast Concrete Sandwich Panels under Axial Loads

AbstractThis paper presents a numerical model developed to predict the response of partially composite load bearing concrete sandwich panels under axial loads applied to the structural wythe at any eccentricity. The model accounts for material nonlinearity, second-order effects, and cracking of concrete and plasticity of steel reinforcement, and can also model fiber-reinforced polymer (FRP) connectors. The analysis uses a bond-slip model to simulate partial composite action between the two wythes resulting from various configurations of insulation and shear connectors. A variety of failure modes can be detected, including concrete crushing, flexural yielding, connectors yielding, pullout or rupture, and stability failures. Progressive failure of connectors is also modeled. The degree of composite action (κu) can be calculated for a given design. The model was verified against experimental data and used to conduct a comprehensive parametric study. It was shown that κu increases with panel length. Connector...

(Invited) Tunnel-Barrier Rectifiers for Optical Nantennas

We present comprehensive experimental and theoretical work on tunnel-barrier rectifiers comprising double (Nb2O5-Al2O3) and triple (Ta2O5-Nb2O5-Al2O3) insulator configurations engineered to enhance low-voltage nonlinearity. The key rectifier properties, asymmetry, nonlinearity and responsivity have been assessed from current-voltage measurements. A superior low-voltage asymmetry (12 at 0.1 V) and responsivity (5 A/W at 0.2 V) for MIIIM rectifiers have been observed. The results demonstrate enhanced rectification by atomically multi-layering tunnel barriers in cascaded and non-cascaded MIIIM arrangements, for inclusion in optical nantennas.

(Invited) Tunnel-Barrier Rectifiers for Optical Nantennas

Thin film metal-insulator-metal (MIM) rectifying devices using double, triple or quadruple insulator layers are currently the focus of attention for the development of next-generation optical nantennas. The interest is driven by their nanoscale footprint, room temperature operation, zero bias voltage requirement, and ease of integration with Complementary Metal Oxide Semiconductor technology. Highly asymmetric and nonlinear current-voltage (IV) behaviour at low applied voltages is critical for these applications. The operation of a MIM device is based on quantum mechanical tunnelling through a thin insulating film positioned between two metal electrodes. Hence, the operation speed of MIM devices depends on the tunneling transmission time, typically in the range of femto seconds or less, and theoretically can reach to a few 100 THz or even into the range of the solar spectrum. Figures of merit for MIM devices include the asymmetry, nonlinearity, and turn-on voltage. Rectification performance in MIM devices is generally limited by the work function difference that can be achieved between the metal electrodes, the barrier heights at either interface, and the mechanism of charge transport through the insulator. The choice of insulator is crucial. Wide band gap insulators provide high turn-on voltage. Narrow band gap insulators, such as Ta2O5 or Nb2O5, are thus attractive since small metal/insulator barrier heights allow for low turn-on voltage. For stable, temperature insensitive, high-speed operation, conduction through the insulator should be dominated by tunneling. In this paper, we present comprehensive experimental and theoretical work on tunnel-barrier rectifiers comprising double (Nb2O5/Al2O3) and triple (Ta2O5/Nb2O5/Al2O3) insulator configurations engineered to enhance low voltage nonlinearity. There are two mechanisms that allow metal-insulator-insulator-metal rectifiers to have a high nonlinearity while keeping the resistance low: (i) resonant tunnelling, and (ii) so-called step tunnelling. Both will be discussed in the paper. A modified multi-layer Tsu-Esaki method has been used for IV calculations from the transmission coefficient by the transmission matrix method. The theoretical work indicates that the onset of resonant tunneling in MIIM and MIIIM rectifiers can be adjusted to close to zero volts by appropriate choice of work function difference of the metal contacts, the thickness of insulator layers, and the depth of quantum well. The double and triple insulator rectifiers were fabricated using atomic layer deposition and rf magnetron sputtering, while the metal contacts including Al and Ag were defined by photolithography or shadow mask and deposited by thermal evaporation. The thickness, band gap, roughness, band offsets, work functions and electron affinities have been extracted from variable angle spectroscopic ellipsometry, atomic force microscopy, x-ray and inverse photoelectron spectroscopy on fabricated devices to ascertain quality of the interfaces and measure barriers. The key rectifier properties, asymmetry, non-linearity and responsivity have been assessed from current voltage measurements performed in the range 293-370 K. A superior low voltage asymmetry (116 at 0.6 V) and responsivity (17 A/W at 0.7 V) for MIIIM rectifiers has been observed in advance of state-of-the-art experimental values. The results demonstrate enhanced rectification by atomically multilayering tunnel barriers in cascaded and non-cascaded MIIIM arrangements, for inclusion in optical nantennas. Acknowledgement. The work has been funded by EPSRC, UK, under project EP/K018930/1.

Towards energy-Efficient homes: Evaluating the hygrothermal performance of different wall assemblies through long-term field monitoring

There is an interest in increasing the energy efficiency of residential housing and sometimes achieving net-zero structures. Effective materials such as spray urethane offer benefits in terms of greater thermal resistance as well as reduction in uncontrolled air leakage. Increased envelope resistance without greatly increasing wall thickness can be a positive feature for a low-energy structure. In this paper, potential hygrothermal performance of five wall panels with different insulation configurations is studied by field experimentation. The five configurations of insulation materials are fibreglass, spray foam, fibreglass with Structural Insulated Sheathing, spray foam EPS rigid insulation, and fibreglass with EPS insulation. The panels are installed side-by-side in a test house; thermocouples and relative humidity sensors are installed. The thermal performance of the panels, humidity levels inside wall cavities, and risk of mold growth are investigated. For further investigation, four homes are constructed, each with one of four potential wall configuration, and studied under occupancy. The experimental results from the building science “building physics” point of view are obtained: wood stud is a thermal bridge on north walls but a thermal mass on west walls; and air cavity in spray foam wall does not generate negative heat convection but increases wall insulation.

Investigation of the freeze–thaw states of foundation soils in permafrost areas along the China–Russia Crude Oil Pipeline (CRCOP) route using ground-penetrating radar (GPR)

The China–Russia Crude Oil Pipeline (CRCOP) was built to transport Siberian crude oil across 1030km of frozen ground. The Chinese portion of the CRCOP crosses 441km of discontinuous permafrost zones along the eastern flanks of the Da Xing'anling (Hinggan) Mountains. Significant thaw settlement of some of the pipeline foundation soils has occurred since the pipeline began operating in January 2011. The differential thaw settlement around the pipeline at the transitions between the thaw-settling and thaw-stable zones may lead to displacement or even buckling of the pipeline. To evaluate the engineering safety and long-term stability of pipeline foundations, ground-penetrating radar (GPR) was used to detect the freeze–thaw states of pipeline foundation soils in the permafrost zones. From April 2012 to November 2013, a total of 2780m of GPR profiles and 62 cross-sections (perpendicular to the CRCOP route) were obtained at eight GPR study sites on various terrains and vegetative coverage, with different thermal insulation configurations around the pipe, and with and without thermosyphons installed. The GPR profiles were interpreted and cross-checked with data from drilling, hand-dug pit or trench excavations, and ground temperature measurements. The results showed that the foundation soils around the pipeline were thawing, with maximum thaw depths under the pipeline of about 1.1m to 4.5m from the pipe bottom and increased maximum thaw depths of 0.5m to 3.7m during the period of this study. However, GPR profiles from the areas with dense vegetative coverage, and with pipe insulation of 80-mm-thick extruded polystyrene (XPS), and also with vertical thermosyphons installed, showed that permafrost foundation soils were thermally better protected, with only minor thaw settlement. The thermal states of pipeline foundation soils and the underlying permafrost varied markedly with different terrains. The drainage patterns and engineering activities, especially the heating from operating oil flows at an average annual oil temperature of 7.7°C (with a range of 0.7°C to 20.4°C) along the pipeline route may have been responsible for the extensive and substantial thaw subsidence in the ice-rich permafrost zones. Additionally, there was positive feedback between the thaw subsidence of ground surface in the vicinity of the pipeline route and the thaw settlement of the pipeline foundation soils. The greater the earth surface subsidence, the more surface water ponding and soil disturbances, and even more progressive thawing. Therefore, some measures are recommended for stabilizing the pipeline foundation soils. The research results also indicate that the GPR method is effective, nondestructive, and convenient for evaluating the spatiotemporal extent and development processes of the freeze–thaw states of pipeline foundation soils and the underlying permafrost.

Empirical flashover model of EHV post insulators based on ISP parameter in cold environments

The main objective of this contribution is to present an empirical model of ice-covered insulator flashover in accordance with an important flashover index, called icing stress product (ISP). The ISP as the product of the ice mass per centimeter of insulator length and the electrical conductivity of the melted ice accretion is used to establish an empirical model to determine the flashover voltage under icing conditions. To achieve this model, several tests were carried out on post station insulators typically used in Hydro-Quebec 735-kV substations, under DC and AC voltage, to determine the relationship between flashover stress and the ISP. The ISP-based method offers a good tool not only to select insulators for locations exposed to freezing conditions, but also to compare flashover results obtained under different test conditions. Moreover, to study the optimizing method of insulator flashover, the influence of air gaps on the flashover stress of ice-covered post insulators is investigated. The results reveal that the number of air gaps significantly affects the flashover stress. The test results are highly meaningful as they can be used as a reference for ranking several other insulator types and configurations in order to select the appropriate one for cold environments. Moreover, several mitigation options to improve insulator reliability in cold environments are provided.

Insulation contamination of overhead transmission lines by extreme service conditions

This paper investigates the specifications of suspended linear insulators under extreme contamination conditions: entrainments of agricultural chemical plants combined with alkaline soil dust. The authors outline the performance properties of insulators with alarge extended surface when contaminated by highly adhesive dust. The authors also give recommendations on the test procedure as well as the selection of optimal insulator configuration for extreme service conditions.

Moisture condensation on building envelopes in differential ventilated spaces in the tropics: quantitative assessment of influencing factors

Ventilation systems play a significant role in maintaining the indoor thermal and hygric balance. Nevertheless, the systems had been implicated to result in many problems. In the tropical climate, especially for energy efficiency purposes, building spaces are operated with differential ventilation. Such spaces operate on 24-hrs basis, some on 8-hrs while others are either naturally ventilated or served with mechanical supply-exhaust fan systems with non-conditioned outdoor air. This practice had been found to result in condensation problems. This study involves a quantitative appraisal of the effect of operative conditions and hygrothermal quality of building envelopes on condensation risk. The in-situ experiment is combined with an analytical approach to assessing the hygrothermal quality of building envelopes in a tropical climate building under differential ventilation between adjacent spaces. The case-studied building is with a known history of condensation and associated damages including mould growth. The microclimate measurement and hygrothermal performance of the wall and floor against condensation and mould growth risks had been previously reported elsewhere. As a step further, the present study evaluates the effects of various envelope insulation types and configurations together with the HVAC cooling set-points on envelope hygrothermal performance. The results revealed that overcooling the air-conditioned side increases condensation risk on the non-air-conditioned side of the envelopes. The envelopes failed criteria for surface condensation at existing operative conditions irrespective of envelope hygrothermal quality improvements. However, the envelope performed well at improved cooling operative conditions even at existing envelope hygrothermal quality. It is, therefore, important to ascertain the envelope hygrothermal quality as well the cooling operative conditions while embarking on energy efficiency operations in mechanical ventilation systems under differential ventilation.

Experimental Study of Cold-Formed Steel Floors Made of Hollow Flange Channel Section Joists under Fire Conditions

AbstractFire safety plays a vital role in building design because appropriate level of fire safety is important to safeguard lives and property. Cold-formed steel channel sections along with fire-resistive plasterboards are used to construct light-gauge steel frame (LSF) floor systems to provide adequate fire resistance ratings (FRR). It is common practice to use lipped channel sections (LCS) as joists in LSF floor systems, and past research has only considered such systems. This research focuses on adopting improved joist sections such as hollow flange channel (HFC) sections to improve the structural performance and FRR of cold-formed LSF floor systems under standard fire conditions. The structural and thermal performances of LSF floor systems made of a welded HFC, LiteSteel Beams (LSB), with different plasterboard and insulation configurations, were investigated using four full-scale fire tests under standard fires. These fire tests showed that the new LSF floor system with LSB joists improved the FRR i...

Mechanism and influencing factors on critical pulse width of oil-immersed polymer insulators under short pulses

The critical pulse width (τc) is a pulse width at which the surface flashover threshold (Ef) is equal to the bulk breakdown threshold (EBD) for liquid-polymer composite insulation systems, which is discovered by Zhao et al. [Annual Report Conference on Electrical Insulation and Dielectric Phenomena (IEEE Dielectrics and Electrical Insulation Society, Shenzhen, China, 2013), Vol. 2, pp. 854–857]. In this paper, the mechanism of τc is interpreted in perspective of the threshold and the time delay (td) of surface flashover and bulk breakdown, respectively. It is found that two changes appear as the pulse width decreases which are responsible for the existence of τc: (1) EBD is lower than Ef; (2) td of bulk breakdown is shorter than td of surface flashover. In addition, factors which have influences on τc are investigated, such as the dielectric type, the insulation length, the dielectric thickness, the dielectrics configuration, the pulse number, and the liquid purity. These influences of factors are generalized as three types if τc is expected to increase: (1) factors causing EBD to decrease, such as increasing the pulse number or employing a dielectric of lower EBD; (2) factors causing Ef to increase, such as complicating the insulator's configuration or increasing the liquid purity; (3) factors causing EBD and Ef to increase together, but Ef increases faster than EBD, such as decreasing the dielectric thickness or the insulation length. With the data in references, all the three cases are verified experimentally. In the end, a general method based on τc for solid insulation design is presented and the significance of τc on solid insulation design and on solid demolition are discussed.

Leader propagation models of ultrahigh-voltage insulator strings based on voltage/time curves under negative lightning impulses at high altitude

Lightning protection analysis is the foundation of estimating the lightning protection behaviors of transmission lines. The lightning flashover criteria of insulators/gaps are an important part of such analysis. One lightning flashover criterion of an insulator/gap is the leader propagation model recommended by CIGRE; however, this model does not consider altitude or longer gaps/insulators (>5 m). In this paper, the 50% disruptive-discharge voltage U50% and 50% voltage/time curve for an air gap of 7.1 m configured by a composite V-string and composite I-string of 7.1 m were measured under negative lightning impulses at the National Engineering Laboratory for Ultrahigh-Voltage Engineering Technology (Kunming), at an altitude of about 2100 m. The insulator types and configurations are similar to those used in the +800kV Ultrahigh-voltage Direct Current (UHVDC) power transmission project. The experimental result shows that the 50% disruptive voltage U50% of the V-string is 7% higher than that of the I-string, and the best-fitting constants of the new leader propagation model of the V-string are different from those of the I-string. The two 50% voltage/time curves were compared with the voltage/time curves predicted by the leader propagation model recommended by CIGRE. The best-fitting constants in leader propagation models are proposed to be used for long air gaps of the V-string insulator and longer I-string composite insulator at high altitude. The new models are verified for a 1.9 m air gap in parallel with a 2.04 m composite insulator and 2.04 m I-string composite insulator.

Modeling of Thermal Phenomena and Economic Aspect of Configuring Furnace Graphite Insulation

The effect of long-term heating on the graphite thermal insulation of a chamber furnace is considered. Mathematical modeling of the process is performed with the help of the ANSYS-FLUENT software. The formation of surface layers is analyzed from the standpoint of economy by comparing furnaces with advanced configuration of the thermal insulation and with the traditional thermal insulation of chamber furnaces. The configuration of the graphite thermal insulation of a furnace is optimized in terms of the heat treatment cost.

Effect of profiles on ac contamination flashover performance of large-tonnage suspension disc insulators

From field experience and laboratory experiments, it was indicated that the flashover performance of contaminated insulators was significantly influenced by the insulator geometry. In the paper, insulators with three different profiles including seven types of deep under-ribs disc insulator, three types of two-shed disc insulator and three types of three-shed disc insulator were tested in an artificial climate chamber to investigate the influences of insulator profile parameters on the flashover performance of large tonnage disc insulators. The artificial contamination test results indicated that 50% flashover voltage stress (E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50%</sub> ) decreased with the increasing insulator diameter and creepage distance. The influence of salt deposit density (SDD) was also investigated, and it was found that E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50%</sub> of alternating-shed insulator decreased more rapidly than that of deep under-ribs insulator with the increase of SDD. An empirical expression was proposed, by employing the least-square method, to describe the relationships between E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50%</sub> and insulator configuration parameters as well as SDD. Through analyzing the generalized fitting coefficients (r) of the equation and the standard error of estimate (s), it can be concluded that the calculated results are in good agreement with the experimental data. Moreover, special attentions were also paid to the influence of the under-ribs and the ratio of shed overhang distance to the shed spacing on flashover performance respectively. This work can enrich the investigation of insulators parameters and may provide useful reference for performance evaluation and selection of insulators in EHV and UHV transmission lines.

Natural ventilation in Beirut residential buildings for extended comfort hours

This paper examines the effectiveness of natural ventilation in Beirut for the purpose of extending comfort periods within living and sleeping zones of the residential buildings. A field survey is conducted to estimate the common window opening and degree profiles. A base case model representing a typical residential apartment located in Beirut was then adopted in integrated environmental solutions (IES) software and calibrated by experimentation through monitoring simulated and measured data indoor. The calibrated IES model was used to evaluate typical wall layering and building local materials and their role in improving indoor comfort with natural ventilation. The simulation results showed that an optimal wall configuration of higher insulation and capacitance, comprised of a 5 cm layer of strawboard sandwiched between a 2 cm × 10 cm wall of masonry Hempcrete units, achieved the highest degree of thermal comfort and enhanced comfort in winter season when compared to the base case.

Foundation heat transfer analysis for buildings with thermal piles

Thermal piles or thermo-active foundations utilize heat exchangers embedded within foundation footings to heat and/or cool buildings. In this paper, the impact of thermal piles on building foundation heat transfer is investigated. In particular, a simplified analysis method is developed to estimate the annual ground-coupled foundation heat transfer when buildings are equipped with thermal piles. First, a numerical analysis of the thermal performance of thermo-active building foundations is developed and used to assess the interactions between thermal piles and slab-on-grade building foundations. The impact of various design parameters and operating conditions is evaluated including foundation pile depth, building slab width, foundation insulation configuration, and soil thermal properties. Based on the results of a series of parametric analyses, a simplified analysis method is presented to assess the impact of the thermal piles on the annual heat fluxes toward or from the building foundations. A comparative evaluation of the predictions of the simplified analysis method and those obtained from the detailed numerical analysis indicated good agreement with prediction accuracy lower than 5%. Moreover, it is found that thermal piles can affect annual building foundation heat loss/gain by up to 30% depending on foundation size and insulation level.

Thermal load mitigation and passive cooling in residential attics containing PCM-enhanced insulations

Residential attics has the potential to be one of the most energy efficient building components by combining thermal processes of attic floor insulation, attic air space, ventilation in attics, and solar collecting roof decks. Large amounts of solar energy collected by the roofs in cooling-dominated and mixed climates generate excess cooling loads, which need to be removed from the building by the space conditioning systems. This paper investigates potential ways to improve the thermal design of the residential home attics to minimize the cooling energy consumption in the cooling-dominated and mixed climates. Dynamic thermal characteristics of thick attic floor insulations and blends of phase change materials (PCMs) with insulations are analyzed. Both approaches can provide notable reductions of thermal loads at the attic level. In addition, a significant time shift of peak-hour loads can move a major operation time for air conditioning system from the daytime peak hours to nighttime low demand hours. A reverse heat flow direction can be observed during the day in the case of really thick layers of bulk insulation or PCM-enhanced insulations, compared to the rest of the building envelope components. This effect may provide free passive cooling to the building, and can be very useful in locations of double electrical tariffs with high daytime peak-hour electric energy rates and less-expensive off-peak energy cost. In both of the above cases, an addition of PCM to the bulk insulation brings substantial performance enhancement not available for traditional insulation applications. This paper presents a short overview of dynamic material characteristics and energy performance data necessary for future dynamic applications of different configurations of the attic floor insulation and PCM-insulation blends in residential homes. A series of whole-building scale and material scale numerical simulations were performed on a single story ranch house to analyze potential energy savings and optimize location of PCM within the attic insulation.