THIS ARTICLE PRESENTS THE MECHANICAL RESPONSES OF PINUS RADIATA WOOD THAT WAS IMPREGNATED WITH OCTADECANE TO OBTAIN A SHAPE-STABILIZED PHASE CHANGE MATERIAL (PCM). PCMS ARE USED AS HEAT STORAGE MATERIALS TO REDUCE THE TEMPERATURE PEAKS AND DISPLACE THE THERMAL LOADS IN AN ENCLOSED SPACE. IT IS IMPORTANT TO STUDY THE EFFECT OF PCMS ON THE MECHANICAL PROPERTIES OF WOOD, SINCE THESE COMPOSITE MATERIALS ARE INTENDED TO BE USED AS A STRUCTURAL MATERIALS IN LOW-THERMAL-MASS HOUSING, WHEREIN A REDUCTION IN MECHANICAL PROPERTIES CAN GENERATE STRUCTURAL RESISTANCE PROBLEMS. FOR THIS PURPOSE, TENSILE AND COMPRESSION TESTS WERE PERFORMED IN THE THREE PRINCIPLE DIRECTIONS (LONGITUDINAL, RADIAL, AND TANGENTIAL) AND BENDING TESTS WERE PERFORMED IN THE LONGITUDINAL DIRECTION. THESE MECHANICAL TESTS WERE CARRIED OUT USING NON-IMPREGNATED WOOD AND PCM-IMPREGNATED WOOD, WHICH WAS FABRICATED USING A DOUBLE VACUUM METHOD CONSISTING OF ALTERNATELY APPLYING A VACUUM AND ATMOSPHERIC CONDITIONS. DIFFERENT IMPREGNATION YIELDS COULD BE VISUALIZED USING COMPUTERIZED MICROTOMOGRAPHY, AND DIFFERENT MECHANICAL BEHAVIORS IN THE THREE PRINCIPLE DIRECTIONS WERE OBSERVED; THE RESULTS SHOWED AN ORTHOTROPIC BEHAVIOR. HOWEVER, THE LONGITUDINAL DIRECTION EXHIBITED THE HIGHEST MECHANICAL RESISTANCE. IN GENERAL, THE STATISTICAL TESTS SHOWED THAT THE MECHANICAL PERFORMANCES OF THE WOOD SAMPLES WERE NOT AFFECTED BY OCTADECANE IMPREGNATION.

COLLAPSE IS ALMOST CERTAIN TO OCCUR IN THE INDUSTRIAL DRYING OF EUCALYPTUS NITENS AND, AS SUCH THIS PREVENTS THE LUMBER MANUFACTURING INDUSTRY IN CHILE FROM PRODUCING COMMERCIAL SOLID WOOD PRODUCTS FROM THIS SPECIES. THIS PROBLEM IS STILL UNSOLVED, AND DIFFERENT STUDIES TO REDUCE COLLAPSE ARE CURRENTLY UNDERWAY. IN THIS EXPLORATORY STUDY, SHRINKAGE AND COLLAPSE AFTER DRYING OF EUCALYPTUS NITENS WAS MEASURED FOR BOARDS CUT FROM DIFFERENT RADIAL LOCATIONS WITHIN THE STEM (CORE, TRANSITION, AND OUTER WOOD FROM PITH TO BARK) AND HAVING DIFFERENT ANNUAL RING ORIENTATIONS (FLAT-SAWN AND QUARTER-SAWN). THOUGH EXPLORATORY, THE RESULTS APPEAR TO CONFIRM THAT PIECES THAT WERE CUT FROM THE CENTER OF THE TREES WERE LESS SUSCEPTIBLE TO COLLAPSE THAN PIECES CUT FROM THE TRANSITION ZONE BETWEEN THE CENTER AND THE PERIPHERY. ON AVERAGE, COLLAPSE IN TRANSITION WOOD WAS APPROXIMATELY 50% HIGHER THAN THE COLLAPSE OBSERVED IN WOOD CUT FROM THE CENTRAL ZONE OF THE TREES.

THE MAIN OBJECTIVE OF THE PRESENT WORK IS THE DEVELOPMENT OF AN ORIGINAL TWO-DIMENSIONAL NUMERICAL SIMULATION OF WOOD DRYING, BASED ON THE WATER POTENTIAL CONCEPT USING THE CONTROL VOLUME FINITE ELEMENT METHOD (CVFEM). THE MATHEMATICAL MODEL WAS BASED ON A SET OF NON-LINEAR SECOND PARTIAL DIFFERENTIAL EQUATIONS, WHICH WERE SOLVED BY A NUMERICAL PROCEDURE USING CVFEM. RESULTS OF DRYING CURVES AND ISOCONCENTRATIONS ARE SHOWN FOR ASPEN (POPULUS TREMULOIDES) SAPWOOD AND COMPARED WITH NUMERICAL AND EXPERIMENTAL DATA. FURTHERMORE, THE IMPACT OF THE VARIATION OF VARIOUS NUMERICAL PARAMETERS WAS STUDIED TO EVALUATE THE ALGORITHMS CONSISTENCE. IT HAD BEEN CONCLUDED THAT THE CURRENT NUMERICAL METHOD WAS CONSISTENT AND ALLOWS TO SIMULATE WOOD DRYING SATISFACTORILY RESULTING IN DETAILED INFORMATION ABOUT WOOD MOISTURE CONTENT DISTRIBUTION.

NEW EXPERIMENTAL DATA IS PRESENTED FOR THE MECHANO-SORPTIVE COEFFICIENT OF EUCALYPTUS NITENS WOOD ANALYZED IN THE LONGITUDINAL DIRECTION THROUGH THE PRINCIPLE OF TOTAL DEFORMATION SUPERPOSITION. THE PROCEDURE WAS BASED ON THE DETERMINATION OF THE PARTIAL STRAIN COMPONENTS: ELASTIC STRAIN, FREE SHRINKAGE STRAIN, AND MECHANO-SORPTIVE STRAIN. THE METHODOLOGY INCLUDED THE DESIGN OF CANTILEVER FLEXION TESTS OF A WOODEN BEAM IN AN AIR-CONDITIONED ENVIRONMENT WITH VARIABLE RELATIVE HUMIDITY. THESE CONDITIONS MADE IT POSSIBLE TO ESTIMATE EACH OF THE DEFORMATION COMPONENTS SEPARATELY AND THEN TO DETERMINE THE MECHANO-SORPTIVE COEFFICIENT USING THE RHEOLOGICAL STRESS-STRAIN MODEL. DEFORMATIONS AND DISPLACEMENTS WERE EVALUATED WITH EXTENSOMETERS AND DISPLACEMENT SENSORS, RESPECTIVELY, IN CONDITIONS OF 0 TO 30% OF THE BREAKING LOAD APPLIED PERPENDICULARLY TO BEAMS ORIENTED IN THE LONGITUDINAL DIRECTION. THE CROSS-SECTION WAS POSITIONED ACCORDING TO THE RELATION BETWEEN THE ACTION LINE OF THE LOAD APPLIED AND THE GROWTH RINGS ORIENTATION. THE VARIATION OF MOISTURE CONTENT WAS CONSIDERED, DECREASING FROM 22 TO 12%. THE RESULTS EXPOSED A DIRECT PROPORTIONALITY BETWEEN THE INTENSITY OF THE APPLIED LOAD AND THE MECHANO-SORPTIVE STRAINS. THE VALUES DETERMINED FOR MECHANO-SORPTIVE COEFFICIENTS WERE 0.1224 AND 0.1746 GPA-1 FOR LOADS APPLIED TO RADIAL AND TANGENTIAL DIRECTIONS, RESPECTIVELY.

CANELO WOOD IS A HIGHLY VALUED NATIVE SPECIES IN CHILE THAT SHOWS DELICATE MARBLING PATTERNS WITH A PINKISH SOFT SILVER LUSTER. DUE TO ITS DECORATIVE QUALITIES, CANELO WOOD IS DRIED FOR THE MANUFACTURE OF FURNITURE AND MUSICAL INSTRUMENTS. HOWEVER, CANELO WOOD LACKS VESSELS CELLS THAT TYPICALLY TRANSPORT THE WATER IN HARDWOODS. PER ITS DRYING BEHAVIOR, CANELO WOOD IS CONSIDERED A TRANSITION SPECIES BETWEEN HARDWOODS AND SOFTWOODS. THEREFORE, THIS ARTICLE REPORTS DRYING SCHEDULES THAT WERE DEVELOPED FOR DRYING 25-MM AND 50-MM CANELO LUMBER. IN ADDITION, THIS ARTICLE REPORTS EXPERIMENTAL OVERALL MASS TRANSFER COEFFICIENTS, SO THAT DRYING TIMES FOR EACH OF THE DRYING STAGES CAN BE EASILY ESTIMATED.

CHILE EXHIBITS A CONTINUOUS GROWTH OF ENERGY DEMAND, AND FOR THIS REASON ENERGY SAVING APPROACHES IN THE COMMERCIAL, PUBLIC, AND RESIDENTIAL SECTORS, WHICH SHARE 21% OF THE FINAL ENERGY CONSUMPTION IN CHILE, HAVE BEEN ENCOURAGED. ONE OF THE SOLUTIONS TO INCREASE ENERGY SAVINGS IN BUILDINGS AND DWELLINGS IS TO INCREASE THE THERMAL PERFORMANCE OF THEIR ENVELOPE. THE USE OF PHASE CHANGE MATERIALS (PCMS) HAS GAINED ATTENTION DURING RECENT YEARS, ESPECIALLY IN NORTHERN CLIMATES, SINCE THEY CAN BE USED TO ENHANCE THE THERMAL INERTIA OF LIGHT BUILDING MATERIALS. USUALLY, THE THERMAL ENVELOPE OF A DWELLING IN CHILE IS MADE OF BRICK OR WOOD TOGETHER WITH LIGHT BUILDING MATERIALS SUCH LIKE FIBER-CEMENT, PLASTERBOARD, AND THERMAL INSULATING MATERIALS AS POLYSTYRENE FOAM. THE EXPERIMENTAL PART OF THIS WORK DEALS WITH THE THERMAL CHARACTERIZATION OF AN ORGANIC PCM (HEXADECANE), WHICH HAS A RELATIVELY LOW PHASE TRANSITION TEMPERATURE. THE CHARACTERIZATION INVOLVES THE MEASUREMENT OF DENSITY, THERMAL CONDUCTIVITY, AND HEAT CAPACITY AS A FUNCTION OF TEMPERATURE, AND THE DETERMINATION OF PHASE CHANGE TEMPERATURE AND LATENT HEAT. THE THERMOPHYSICAL PROPERTIES WERE IMPLEMENTED IN A SET OF THERMAL SIMULATIONS OF AN ACTUAL PROJECT DWELLING LOCATED IN SANTIAGO AND PUERTO MONTT. THE NUMERICAL RESULTS IN TERMS OF HEAT STORAGE AND TEMPERATURE PROFILES IN THE ENVELOPE, AND HEATING AND COOLING DEMANDS ARE SHOWN FOR DIFFERENT INSULATION LEVELS.

TO EVALUATE EVOLUTION OF PHYSICAL AND MECHANICAL PROPERTIES DUE TO DRYING AND HEAT MODIFICATION, A LOAD OF RADIATA PINE WOOD WAS SELECTED AND PROPERTIES WERE MEASURED AFTER EACH DRYING PROCESS. THE RESULTS REVEALED INTERESTING CORRELATIONS BETWEEN INTRINSIC FACTORS AND PROPERTIES; THE VALUES OF DENSITY WERE HIGHLY DISPERSED AFTER DRYING OR THERMAL TREATMENT AND UNCORRELATED WITH OTHER PARAMETERS, BUT THE MINIMUM DENSITY VALUES WERE KEPT CONSTANT AFTER HEAT TREATMENT. MOREOVER, WEIGHT LOSS (WL) AND MOISTURE CONTENT (MC) WERE DECREASING PROPORTIONALLY TO THE TREATMENT INTENSITY, DUE TO WOOD?WATER INTERACTIONS, CELL WALL CHANGES, AND THERMAL DEGRADATION OF WOOD FRACTIONS. WL AND MC WERE REASONABLY CORRELATED WITH THE DIMENSIONAL STABILITY, IMPROVING THE DIMENSIONAL STABILITY AFTER DRYING TREATMENTS, BUT KEEPING THE SAME ORDER OF ANISOTROPY. REGARDING THE WOOD STIFFNESS (MODULUS OF ELASTICITY, MOE), IT WAS UNAFFECTED BY THE DRYING TEMPERATURE, AND THE CORRELATIONS BETWEEN MOE AND MC OR WL APPEAR TO BE ACCEPTABLE, AND THE VALUES OF MC OR WL DID NOT ADVERSELY AFFECT THE MOE. HOWEVER, THE MODULUS OF RUPTURE WAS DROPPED DURING THE DRYING PROCESS, OBTAINING THREE DIFFERENTIATED GROUPS WITH A DECREASE IN AROUND 59% AFTER THERMAL MODIFICATION.

THIS ARTICLE REPORTS THE RESULTS OF AN EXPLORATORY STUDY DESIGNED TO REDUCE HEAT AND ELECTRICITY CONSUMPTION IN INDUSTRIAL DRYING OF RADIATA PINE. THE EXPERIMENTS WERE PERFORMED WITH SLIGHT MODIFICATIONS OF THE STANDARD DRYING SCHEDULES USED BY THE SAWMILL TO DRY RADIATA PINE IN 100-M3 INDUSTRIAL KILNS. THE HEAT AND ELECTRICITY CONSUMPTION WERE DETERMINED WITH DATA COLLECTED DURING THE DRYING RUNS AND CALCULATIONS BASED ON MATHEMATICAL MODELS. THE RESULTS SHOWED THAT DEPENDING ON THE CASE, HEAT AND POWER CONSUMPTION WERE RESPECTIVELY REDUCED BY UP TO 14 AND 35%.

COLLAPSE AND DRYING STRESSES ARE CURRENTLY INDUCED DURING THE DRYING OF EUCALYPTUS NITENS IN SOLID WOOD PRODUCTS. THE PURPOSE OF THIS STUDY WAS TO INVESTIGATE THESE DRYING STRESSES BY MEASURING HYGROMECHANICAL STRAINS DURING THE DRYING OF EUCALYPTUS NITENS BOARDS. SMALL SAMPLES OF EUCALYPTUS NITENS WOOD WERE ORIENTED IN THE RADIAL AND TANGENTIAL DIRECTIONS AND TESTED TO DETERMINE THE HYGROMECHANICAL STRAINS DURING THE DRYING PROCESS. THIS EXPERIMENTAL WORK CONSISTED OF CANTILEVERED BENDING TESTS CONDUCTED UNDER VARIABLE RELATIVE HUMIDITY CONDITIONS. TESTS WERE PERFORMED IN A CONDITIONING CHAMBER AT 30 °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

IN THIS STUDY, THE EFFECTS OF THE WOOD QUALITY USED FOR THERMAL MODIFICATION ON THE PHYSICAL AND MECHANICAL PROPERTIES OBTAINED AT TWO TREATMENT TEMPERATURES COMMONLY USED AT THE INDUSTRIAL LEVEL WERE EVALUATED IN ORDER TO VALIDATE EXPERIMENTALLY THE PILOT SCALE PROCESS FOR ITS FUTURE INDUSTRIAL SCALING. THE QUALITY OF THE INPUT RADIATA PINE REFERS TO THE PRESENCE OF NATURAL DEFECTS OF WOOD, AS WELL AS THE AMOUNT OF JUVENILE WOOD. SELECTED THERMALLY MODIFIED SAMPLES WERE USED TO MEASURE SOME QUALITY MARKERS (PHYSICAL, MECHANICAL, OPTICAL) AND TO FIND THEIR CORRELATIONS DUE TO QUALITY OR TREATMENT, SO AS TO OBTAIN THE BEST CHARACTERISTICS OF THE HEAT-TREATED PRODUCTS. THE RESULTS INDICATED THAT THE QUALITY OF THE INPUT WOOD WAS ONLY RELEVANT TO THE MILD TREATMENT (190 °C), FINDING AN ACCEPTABLE CORRELATION BETWEEN THE WEIGHT LOSS AND THE QUALITY USED (FIRST QUALITY). AFTER BOTH TREATMENTS, THE ORDER OF ANISOTROPY WAS KEPT AND THE DIMENSIONAL CHANGES WERE SIGNIFICANTLY REDUCED; THUS, THE WEIGHT LOSS DURING TREATMENT DID NOT DRAMATICALLY AFFECT ITS ANATOMICAL STRUCTURE. CLUSTERING THE DATA BY STATISTICAL PROCEDURES WAS POSSIBLE TO OBSERVE THAT SAMPLES OF LOWER QUALITY WERE ORDERED ACCORDING TO THE TREATMENT TEMPERATURE, INDICATING A STRONG INFLUENCE OF THE TREATMENT ON THE PROPERTIES OBTAINED. THE MECHANICAL PROPERTIES REVEALED THAT UP TO 190 °C THE CHEMICAL CHANGES THAT OCCUR ON WOOD AFFECTED POSITIVELY THE VALUES (MOE INCREASED BY ABOUT 15?32% AND MOR SLIGHTLY DECREASED?

LABORATORY SCALE EXPERIMENTS ARE PERFORMED IN ORDER TO CHARACTERIZE THE ARTIFICIAL WOOD DRYING OF PINUS RADIATA AT CONVENTIONAL TEMPERATURES AND ACCELERATED TEMPERATURES. THE EXPERIMENTAL DATA ALLOW DETERMINING THE WOOD THERMAL CONDUCTIVITY THROUGH INVERSE METHODOLOGY. THE COMPARATIVE ANALYSIS SHOWS THAT THE IMPLEMENTATION OF THE DEVELOPED INVERSE METHODOLOGY IS CONSISTENT WITH INFORMATION AVAILABLE IN THE SPECIALIZED LITERATURE; WHICH MEANS INCREASED THERMAL CONDUCTIVITIES WITH INCREASED HUMIDITY AND TEMPERATURE, WHOSE VALUES OSCILLATE BETWEEN 0,34 AND 0,56 (W/M K) TO MOISTURE VARIATIONS BETWEEN 22% AND 64%; AND TEMPERATURES BETWEEN 70°C AND 90°C, RESPECTIVELY.

THIS PAPER REPORTS ON THE PROPERTIES OF PINUS RADIATA WOOD IMPREGNATED WITH AN ORGANIC PHASE CHANGE MATERIAL (O-PCM). THE TESTS ARE AIMED AT CHARACTERIZING THE KINETICS OF IMPREGNATION (RATES, FLOWS, AND FRONTS) AND THE THERMOPHYSICAL PROPERTIES (THERMAL CONDUCTIVITY AND SPECIFIC HEAT). IN PARTICULAR, A PARAFFIN TYPE O-PCM (OCTADECANE) IS USED TO IMPREGNATE DRY RADIATA PINE WOOD IN THE TANGENTIAL FLOW DIRECTION AT FOUR MANOMETRIC PRESSURES (0, 1, 2, AND 3 BAR) AND CONSTANT TEMPERATURE OF 50 °C. THE WOOD IS SAPWOOD FROM 12-YEAR OLD P. RADIATA GROWING IN THE BÍO-BÍO REGION AND DIMENSIONED ACCORDING TO CHILEAN STANDARD FOR TREATED WOOD SAMPLE EXTRACTION. THE RESULTS SHOW THAT IT IS VIABLE TO IMPREGNATE P. RADIATA WOOD WITH O-PCM TO IMPROVE ITS THERMOPHYSICAL PROPERTIES WITH THE PURPOSE OF PASSIVE CONDITIONING.

WE MODELED CONVENTIONAL ONEDIMENSIONAL DRYING OF RADIATA PINE (PINUS RADIATA) WOOD USING THE CONCEPT OF EFFECTIVE DIFFUSION. THE EXPERIMENTALLY DETERMINED EFFECTIVE DIFFUSION COEFFICIENTS FOR THE RADIAL AND TANGENTIAL DIRECTIONS WERE RELATED EXPONENTIALLY TO THE MOISTURE CONTENT. THESE COEFFICIENTS WERE CHARACTERIZED BY TWO PARAMETERS THAT WERE DETERMINED THROUGH OPTIMIZATION WITHIN THE CONTEXT OF AN INVERSE PROBLEM. ONE-DIMENSIONAL DRYING EXPERIMENTS WERE CARRIED OUT UNDER CONSTANT DRYING 44/36 (ºC/ºC) IN ORDER TO DETERMINE TRANSITORY SPATIAL DISTRIBUTIONS OF MOISTURE AND DRYING CURVES, WHICH WERE USED THEN TO DETERMINE THE MODEL PARAMETERS AND VALIDATE THE MODEL. THE MATHEMATICAL MODEL CONSISTED OF A PARTIAL, NON-LINEAR, DIFFERENTIAL EQUATION OF THE SECOND ORDER AND WAS CHARACTERIZED BY COEFFICIENTS THAT VARIED EXPONENTIALLY WITH MOISTURE CONTENT; THIS LATER WAS INTEGRATED NUMERICALLY THROUGH THE FINITE VOLUME METHOD. SIMULATIONS OF THE TRANSITORY DISTRIBUTION OF MOISTURE GRADIENTS GAVE SATISFACTORY RESULTS, AND THE DRYING CURVES WERE CORRELATED WITH EXPERIMENTAL DATA AS WELL AS THE VALUES OF THE PARAMETERS REQUIRED BY THE PROPOSED MODEL.

WE MODELED CONVENTIONAL TWO-DIMENSIONAL DRYING OF RADIATA PINE (PINUS RADIATA) WOOD USING THE CONCEPT OF EFFECTIVE DIFFUSION EXTENDED TO OVERALL DRYING PROCESS. EFFECTIVE DIFFUSION COEFFICIENTS WERE DETERMINED EXPERIMENTALLY ON THE TRANSVERSAL PLANE AND DEPENDED EXPONENTIALLY ON THE MOISTURE CONTENT. THESE COEFFICIENTS WERE CHARACTERIZED BY TWO PARAMETERS DETERMINED THROUGH OPTIMIZATION WITHIN THE CONTEXT OF AN INVERSE PROBLEM. SPATIALLY VARIABLE CONVECTION COEFFICIENTS WERE DETERMINED IN THE SAME MANNER. EXPERIMENTS USING CONSTANT DRYING 44/36 (ºC/ºC) WERE CARRIED OUT IN ORDER TO DETERMINE TRANSITORY SPATIAL DISTRIBUTIONS OF MOISTURE AND DRYING CURVES, WHICH WERE THEN USED TO DETERMINE AND VALIDATE THE MODEL PARAMETERS. THE MATHEMATICAL MODEL CONSISTED OF A PARTIAL, NON-LINEAL, DIFFERENTIAL EQUATION OF THE SECOND ORDER, WAS CHARACTERIZED BY COEFFICIENTS THAT VARIED EXPONENTIALLY WITH MOISTURE CONTENT, INTEGRATED NUMERICALLY THROUGH THE FINITE VOLUME METHOD. RESULTS OF TWO-DIMENSIONAL SIMULA-TIONS FOR ISOTHERMAL DRYING OF RADIATA PINE TIMBER, CORRELATED WITH EXPERIMENTAL DATA, ARE SHOWN: A) TRANSITORY DISTRIBUTION OF MOISTURE GRADIENTS, B) DRYING CURVES AND C) PARAMETER OF MATHEMATICAL MODEL (EFFECTIVE DIFFUSION AND MASS CONVECTION COEFFICIENTS).

THE PRESENT WORK STUDIED THE NUMERICAL MODELLING OF HEAT TRANSFER IN A PILE OF PINUS RADIATA SAMPLES OF A SQUARE CROSS-SECTION BY USING RADIO FREQUENCY HEATING. MORE PRECISELY, THE STUDY FOCUSED ON THE EFFECTS OF THE ENERGY TRANSFERRED TO A DIELECTRIC MATERIAL (WOOD) FROM AN ELECTROMAGNETIC FIELD, WHICH REQUIRED THE CALCULATION OF THE DIELECTRIC LOSS FACTOR AND ITS CORRELATION WITH CONSERVATIVE EQUATIONS. IN THIS WAY, THE TEMPERATURE DISTRIBUTION ACROSS PINUS RADIATA SAMPLES WAS OBTAINED THROUGH THE INTEGRATION OF THE ENERGY EQUATION USING THE FINITE VOLUME METHOD. THE NUMERICAL RESULTS WERE COMPARED TO EXPERIMENTAL DATA OBTAINED FROM THREE EXPERIMENTS OF RADIO-FREQUENCY HEATING OF WOOD SAMPLES OF A CROSS-SECTIONAL AREA OF 4 IN × 4 IN, 3.1-M-LONG, AND 20 CM OF SEPARATION BETWEEN PLATES. ACCORDING TO THE OBSERVED LINEAR BEHAVIOR OF THE HEAT TRANSFER PROCESS, THE NUMERICAL RESULTS OF THE TRANSIENT VARIATION OF TEMPERATURE WERE IN AGREEMENT WITH THE EXPERIMENTAL DATA.

NUMERICAL PREDICTION OF HEAT TRANSFER BY NATURAL CONVECTION OF A HERSCHEL-BULKLEY NON-NEWTONIAN FLUID INSIDE A SQUARE CAVITY HAS BEEN COMPUTATIONALLY ANALYZED. UNSTEADY 2D FLUID MECHANICS AND HEAT TRANSFER WERE DESCRIBED IN TERMS OF THE NON-LINEAR COUPLED CONTINUITY, MOMENTUM AND HEAT EQUATIONS. THESE EQUATIONS WERE SOLVED BY THE CONTROL VOLUME FINITE ELEMENT METHOD (CVFEM) WITH GAUSS-SEIDEL/ SYSTEM OVER-RELAXATION COUPLING ALGORITHM. THE EFFECT OF THE RA, PR, BN AND THE RHEOLOGICAL BEHAVIOR INDEX (N) ON THE NON-NEWTONIAN FLUID THERMAL AND MOMENTUM BEHAVIOR WERE STUDIED. THE NON-NEWTONIAN FLUID FLOW WAS DESCRIBED BY THE RHEOLOGICAL MODEL OF HERSCHEL-BULKLEY. RESULTS FOR THE STREAMLINES AND ISOTHERMS ALONG THE ENCLOSURE WALLS ARE PRESENTED. IT WAS FOUND THAT THE EFFECT OF THE PR AND BN IS MORE IMPORTANT WHEN THE RA IS LOWER (10(3)). IN ADDITION, THE BEHAVIOR INDEX HAD A SIGNIFICANT EFFECT ON THE CPU TIME FOR THE DIFFERENT STUDIED CASES.

THE DEMAND FOR AIR CONDITIONING AND HEATING IN THE CONSTRUCTION SECTOR HAS INCREASED IN ABOUT TWO DECADES, MAINLY BECAUSE OF DEMOGRAPHIC AND ECONOMIC GROWTH. THE RESULT OF THIS INCREASE IN ENERGY CONSUMPTION HAS BEEN MORE GREENHOUSE GAS EMISSIONS (GHGS). THIS PAPER PROPOSES A MULTI-OBJECTIVE OPTIMIZATION DESIGN THAT HELPS REDUCE HEATING, VENTILATION, AND AIR-CONDITIONING (HVAC) ENERGY CONSUMPTION AND INCREASES THE THERMAL COMFORT LEVELS IN LOW-INCOME HOUSING. ACHIEVING THESE OBJECTIVES REQUIRED CHOOSING A DWELLING UNIT THAT IS REPRESENTATIVE OF THE CHILEAN HOUSING STOCK, WHICH WAS IDENTIFIED WITH THE HELP OF THE NATIONAL HOUSING MONITORING NETWORK (RENAM). THE SELECTED OPTIMIZATION VARIABLES CORRESPOND TO THE TYPE OF WINDOWS, TYPE AND THICKNESS OF CEILING INSULATION, AND TYPE OF PCM-IMPREGNATED PINUS RADIATA WOOD PANEL, WITH PCM MELTING POINTS BETWEEN 8 AND 27 DEGREES C. SUBSEQUENTLY, WE MINIMIZED THE HOURS OF THERMAL DISCOMFORT AND THE DWELLING TYPOLOGY'S ELECTRICAL CONSUMPTION OF HEATING AND COOLING BY USING THE ALGORITHM THE NON-DOMINATED SORTING GENETIC ALGORITHM-II (NSGA-II). THE MAIN RESULTS INCLUDE A REDUCTION OF UP TO 21.5 % IN THE THERMAL DISCOMFORT HOURS AND A DECREASE OF UP TO 80.5 % IN ENERGY CONSUMPTION ASSOCIATED WITH THE OPTIMAL HOUSING TYPOLOGY COMPARED TO THE BASE CASE. ADDITIONALLY, THE ECONOMIC ANALYSIS INDICATED THE PAYBACK PERIOD IS 12.9 YEARS FOR THE PARETO SOLUTION, WHICH PRESENTS A LOWER DISTANCE TO THE UTOPIC POINT (UP).