Effect Of Intermittent Heating Research Articles

Effect of Intermittent Heating on Creep Behaviour of Advanced 9-12%Cr Power Plant Steels

Critical high temperature components of machines and structures are often subjected to complicated load and temperature histories. The closest laboratory simulation of service loading conditions involves creep under nonsteady temperatures and stresses. For example, the start up and shut down cycles can be well simulated by temperature variation by use of intermittent heating tests. Such approach is illustrated by recent experimental results on advanced high creep strength 9- 12%Cr ferritic-martensitic steels (P91, P92 and E911). A comparison between the creep characteristics of nonsteady and monotonously creep specimens has revealed no significant deterioration of the creep strength and fracture resistance of these steels in power-law (dislocation) creep.

The effect of intermittent and continuous heating of soybean oil at frying temperature on the formation of 4‐hydroxy‐2‐trans‐nonenal and other α‐, β‐unsaturated hydroxyaldehydes

Abstract4‐Hydroxy‐2‐trans‐nonenal (HNE) is a cytotoxic secondary lipid peroxidation product of linoleic acid. Previous investigations in this laboratory showed that HNE is formed in thermally oxidized soybean oil, which is high in linoleic acid. Continuous exposure of the oil to frying temperature (185°C) for up to 6 h graduallyincreased the formation of HNE and other polar lipophilic aldehydes. Additional investigations in this laboratory showed that HNE is absorbed into food fried in thermally oxidized oil in the same concentration as was found in the oil. In the present experiment, the effect of intermittent heating on the formation of HNE in soybean oil was compared with continuous heating. Soybean oil samples were heated either for 1 h each day for five sequential days or for 5 h continuously at 185±5°C. The thermally oxidized soybean oil samples were analyzed by HPLC for the presence of HNE and three other polar lipophilic α‐,β‐unsaturated hydroxyaldehydes: 4‐hydroxy‐2‐trans‐hexanal, 4‐hydroxy‐2‐trans‐octenal, and 4‐hydroxy‐2‐trans‐decenal. Under intermittent and continuous heating over a total of 5 h, the concentration of these compounds increased similarly. These results indicate that the formation of HNE and other hydroxyaldehydes at frying temperature is a cumulative result of oxidation of PUFA over time.

The effect of intermittent heating on some chemical parameters of refined oils used in Egypt. A public health nutrition concern

As part of a public health campaign in Egypt, various chemical parameters of oil which are considered good indices in assessing the degree of thermal abuse, oxidation and overall quality (acid values, iodine values, peroxide values, etc.) were studied with respect to different frying oils. Ingestion of decomposition products formed as a results of thermal abuse and oxidation of frying oils are known to lead to a variety of symptoms and diseases (allergies, atherosclerosis, coronary heart disease). Results show that the oil most commonly used by street vendors in Egypt (blend of cotton seed and sunflower oil) is the least suitable for frying, while palm oil on the basis of the various chemical parameters studied, is the ideal choice. However, from the nutritional and public health stand point, the use of saturated oils is to be discouraged. Corn oil is therefore the next best choice from both the chemical and nutritional stand point, and is recommended for public use in a country in which deep-fried vegetable patties (‘fallafel’) forms the staple food item in the diet.

The effect of intermittent heating on fatigue crack growth: Lam, Y.C. and Griffiths, J.R. Theor. Appl. Fract. Mech. Sept. 1990 14 (1), 37–41

The effect of intermittent heating on fatigue crack growth: Lam, Y.C. and Griffiths, J.R. Theor. Appl. Fract. Mech. Sept. 1990 14 (1), 37–41

The effect of intermittent heating on fatigue crack growth

The effects on fatigue crack growth of the application of heat treatment with and without an applied load are discussed. The investigation indicates that when heat treatment is performed simultaneously with an applied load, compressive residual stress will be introduced resulting in better resistance to fatigue crack initiation and growth. Fatigue crack growth tests were performed on single-edge-cracked plates. The fatigue life and crack growth rate for plates with no heat treatment and plates with heat treatment under zero stress are similar. However, for plates with heat treatment carried out under a static load equal to the maximum in the fatigue cycle, the fatigue life increased by 40% and the crack growth rate immediately after heat treatment decreased by 65%.

The effect of intermittent heating on surface temperatures in rooms

This paper presents a simple approximate method of calculating surface temperatures resulting from a repeated square wave heat input to a room. The calculated values are shown to give reasonable agreement with results obtained on an electrical analogue. Values of thermal impedance for single and multi-layer walls are tabulated.

Effect of intermittent heating on the kinetics of photooxidation of anthracene and naphthacene in a polymer matrix

Effect of intermittent heating on the kinetics of photooxidation of anthracene and naphthacene in a polymer matrix

Hy-Therm Copper----An Improved Overhead-Line Conductor

A new brand of copper has been developed which, by virtue of increased resistance to annealing, permits higher current-carrying capacity and longer useful life under load with no significant loss in conductivityv. The annealing characteristic of copper is influenced by a number of factors: 1. The effect on annealing of noncuprous elements is the resultant of a complex interrelationship due to many variables and the net result appears to depend primarily on the ore and refining processes. 2. The effect of continuous heating is to start annealing immediately at a rate depending on the temperature and type of copper. 3. The effect of intermittent heating is directly cumulative. 4. The effect of externally-applied tension is to increase the rate of annealing. These data enable continuous and short-time current-carrying capacities of over-head lines to be calculated more accurately.