Other affiliations: University of São Paulo
Bio: Cláudio Melo is an academic researcher from Universidade Federal de Santa Catarina. The author has contributed to research in topics: Heat exchanger & Oyster. The author has an hindex of 27, co-authored 131 publications receiving 2319 citations. Previous affiliations of Cláudio Melo include University of São Paulo.
Papers published on a yearly basis
TL;DR: In this paper, a semi-algebraic model was proposed to predict the variation of the frost layer thickness and mass with time, based on mass and energy balances within the layer, assuming the frost as a porous medium.
Abstract: The present study advances a theoretical and experimental investigation of the frost growth and densification on flat surfaces. This study focuses on the most important factors affecting the frost formation process, i.e. the surrounding air temperature, humidity and velocity, and the surface temperature. The processes of frost growth and densification were investigated experimentally in order to provide a physical basis for the development of a theoretical model to predict the variation of the frost layer thickness and mass with time. The mathematical model was based on mass and energy balances within the frost layer, assuming the frost as a porous medium and accounting for the supersaturation of the moist air on the frost surface. The governing equations for mass and heat diffusion were integrated analytically, giving rise to a semi-algebraic formulation which requires numerical integration of only one time dependent ordinary differential equation. When compared with experimental data, the model predictions of the frost thickness as a function of time agreed to within ±10% error bands. The experimentally-validated model was then used to predict the frost layer growth and densification with respect to the operation conditions such as plate surface temperature, air stream temperature, humidity and velocity.
TL;DR: In this article, a simplified model to assess the energy performance of vapor compression "on-off" controlled refrigerators is presented, which consists of first-principles algebraic equations adjusted with experimental information obtained from the refrigeration system under study.
Abstract: A simplified model to assess the energy performance of vapor compression ‘on–off’ controlled refrigerators is presented herein. The model consists of first-principles algebraic equations adjusted with experimental information obtained from the refrigeration system under study. The experimental work consisted of controlling and measuring the system and component operating conditions in order to gather key information for the development and validation of the model. The methodology showed similar accuracy to that using more sophisticated dynamic simulation codes, but with lower computational costs. When compared to experimental data, the model predicted AHAM energy consumption tests within a ±5% deviation band. A sensitivity analysis considering the number of tube rows in the condenser coil, the number of fins in the evaporator coil and the compressor stroke is also reported. The refrigeration system under study was a top-mount ‘Combi’ 600-l refrigerator, ‘on–off’ controlled by the temperature of the fresh-food compartment.
TL;DR: In this article, a mathematical model for the heterogeneous frost nucleation on smooth surfaces was put forward based on the classical nucleation theory, which showed a good level of agreement.
Abstract: This paper advances an investigation on the frost nucleation on flat surfaces. The study focuses on the relevant parameters affecting the frost formation process, i.e., the surrounding air temperature and humidity, and the surface conditions (temperature, roughness and contact angle). The process of ice crystal nucleation was investigated both theoretically and experimentally in order to provide the physical basis for a criterion for predicting the occurrence of frost nucleation as a function of the operating conditions and surface characteristics. A mathematical model for the heterogeneous frost nucleation on smooth surfaces was put forward based on the classical nucleation theory. Experiments were carried out using a purpose-built apparatus to acquire data to validate the model. When compared to in-house as well as independent experimental data, the model predictions showed a good level of agreement.
TL;DR: In this article, a first-principles model for simulating the transient behavior of household refrigerators is presented, in which the compressor is on-off controlled by the freezer temperature, while a thermo-mechanical damper is used to set the freshfood compartment temperature.
Abstract: A first-principles model for simulating the transient behavior of household refrigerators is presented in this study. The model was employed to simulate a typical frost-free 440-l top-mount refrigerator, in which the compressor is on–off controlled by the freezer temperature, while a thermo-mechanical damper is used to set the fresh-food compartment temperature. Innovative modeling approaches were introduced for each of the refrigerator components: heat exchangers (condenser and evaporator), non-adiabatic capillary tube, reciprocating compressor, and refrigerated compartments. Numerical predictions were compared to experimental data showing a reasonable level of agreement for the whole range of operating conditions, including the start-up and cycling regimes. The system energy consumption was found to be within ±10% agreement with the experimental data, while the air temperatures of the compartments were predicted with a maximum deviation of ±1 °C.
TL;DR: In this paper, an experimental investigation on the frost accretion of tube-fin evaporators considering the fan characteristics is carried out, and it was found that the frost formation rate increases with the air flow rate, supercooling degree and the density of fins.
Abstract: Compact tube-fin evaporators have been extensively used in refrigeration cassettes for light commercial applications. Such refrigeration systems are space constrained and, therefore, the heat exchangers (condenser and evaporator) must have a large area-to-volume ratio. In addition, such applications require a subfreezing evaporating temperature that induces the growth of a frost layer on the finned surface, which may block the evaporator if a proper defrost strategy is not used. Before completely blocking the evaporator, the frost layer depletes the heat exchanger performance by adding an extra thermal resistance and also by reducing the fan-supplied air flow rate. Understanding the way the frost forms on these compact heat exchangers and also the way the fan is affected by frost clogging is mandatory for the design of robust refrigeration systems and also to devise more efficient defrost strategies. In this study an experimental investigation on the frost accretion of tube-fin evaporators considering the fan characteristics is carried out. To this end, a specially designed, constructed and calibrated closed-loop wind-tunnel facility was used. Experimental tests were carried out with four different (three wavy-fin and one louvered-fin) evaporator coils under different conditions. It was found that the frost formation rate increases with the air flow rate, supercooling degree and the density of fins. A strict relation between accumulated mass of frost, air-side pressure drop and cooling capacity was also observed. It was also noted that the fan characteristics play an important role on the evaporator thermal performance, indicating that under frosting conditions the fan-evaporator pair must be designed as a coupled system. Furthermore, for the same operating conditions, the louvered-fin evaporator showed to be more sensitive to the frost formation effects than the wavy-fin coils.
TL;DR: For the next few weeks the course is going to be exploring a field that’s actually older than classical population genetics, although the approach it’ll be taking to it involves the use of population genetic machinery.
Abstract: So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to
01 Jan 2011
TL;DR: The sheer volume and scope of data posed by this flood of data pose a significant challenge to the development of efficient and intuitive visualization tools able to scale to very large data sets and to flexibly integrate multiple data types, including clinical data.
Abstract: Rapid improvements in sequencing and array-based platforms are resulting in a flood of diverse genome-wide data, including data from exome and whole-genome sequencing, epigenetic surveys, expression profiling of coding and noncoding RNAs, single nucleotide polymorphism (SNP) and copy number profiling, and functional assays. Analysis of these large, diverse data sets holds the promise of a more comprehensive understanding of the genome and its relation to human disease. Experienced and knowledgeable human review is an essential component of this process, complementing computational approaches. This calls for efficient and intuitive visualization tools able to scale to very large data sets and to flexibly integrate multiple data types, including clinical data. However, the sheer volume and scope of data pose a significant challenge to the development of such tools.
01 Jan 2007
15 Feb 2016
TL;DR: Standard methods for the examination of water and wastewater: including bottom sediments and sludges, standard methods for examining water, including bottom sediment and sludge, are described in this paper.
Abstract: Standard methods for the examination of water and wastewater: including bottom sediments and sludges , Standard methods for the examination of water and wastewater: including bottom sediments and sludges , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی