Whenliquidisheateditevaporates.Theevaporationprocessisdependentonpressure,temperatureandcompositionoftheliquidandgas.Gascanalsocondense.Inadditionthereisaconvectiveheattr... When liquid is heated it evaporates. The evaporation process is dependent on pressure, temperature and composition of the liquid and gas. Gas can also condense. In addition there is a convective heat transfer between the liquid and gas zone that must be considered. The surfaces in the gas zone also radiates from the shell to the liquid.
During the blowdown process mass is usually evacuated from the gas zone, but also liquid might be released. The rate of release is dependent on density and pressure as well as the release area.
As pressure and temperature change, the properties of all
materials change. This has to be considered in a prediction of a
blowdown process.
The main purpose of a blowdown process is as earlier
stated to maintain integrity of the equipment. The strength
properties of the shell are the key factor on that matter. The
strength is dependent on the inside pressure as well as the
support forces. If the exposing forces produce stress that
exceeds the ultimate tensile stress (UTS) in some regions, the
integrity of the equipment is no longer maintained. In the
design phase of a process plant, these aspects are crucial and
must be included as a dimensional factor. For that reason prediction of the blowdown process is essential.
Lately some new standards has been introduced to the
industry on this matter [3] and [4].
VessFire [1] and [2] is a multi physics system designed for
calculation of this kind of problems. It has been applied for
some time in the oil and process industry on many projects. The
system satisfies the requirements for predictions outlined in [3]
and [4]. It includes all aspects described above including
integrity of the shell. As part of the verification process some
experiments where performed. Some of the experiments are
presented here.
EXPERIMENTAL STUDY
The purpose of the experiments was to investigate the
evaporation process and the heat transfer to the liquid and
vapour. In a complex system it is important to reduce unknown
parameters as far as possible. Exposure from a flame is difficult
to control. Flux measurements are point values and not
necessarily representative for the average exposure. In order to
control the heat exposure it was decided to apply an electric
heating system. The system and the verification of the system is
described in [5], [6] and [8].
The furnace was built inside a supporting tube. Figure 2 shows
a general arrangement of the experimental outfit. A 0.05 mm
stainless steel foil formed as a tube, 300 mm in diameter,
generated the heat. The power supply was based on a 3-phase
alternating current system giving 48 Volt output as maximum.
The top exposure had a limit of 300 kW. The foil had a surface
of about 1 m2, giving a heat flux up to 300 kW/m2.
The power input could be continuously regulated from zero to maximum load. Each experiment was started from zero and brought up to the required load within a few seconds. After that the surface temperature of the heating foil was kept constant during the exposure period. Experiments with both dry objects as well as water filled object were performed. In this paper only water filled experiments are presented
Figure 2 General arrangements drawing of the experimental furnace including the specimen and its support
Figure 3 Illustration of the heating unit. The black part is copper conductors for the foil. The
grey part is the heating foil exposing the specimen. The foil is equipped with thermo-elements all marked H, except H5 which is the temperature in a copper ring
and H6 which is the temperature between the insulation and the supporting tube.
When liquid is heated it evaporates. The evaporation process is dependent on pressure, temperature and composition of the liquid and gas. Gas can also condense. In addition there is a convective heat transfer between the liquid and gas zone that must be considered. The surfaces in the gas zone also radiates from the shell to the liquid. 当液体被加热时,它就蒸发。蒸发过程与压力、温度和液体及气体的组分有关。气体也可以凝结。除此以外,在液体区和气体区之间还有一种对流热传导必须加以考虑。在气体区的表面(热)还从外壳辐射到液体。
During the blowdown process mass is usually evacuated from the gas zone, but also liquid might be released. The rate of release is dependent on density and pressure as well as the release area. 在排放过程中,物质通常是从气体区排放的,但是也可释放液体。释放速率与密度、压力以及释放面积有关。
As pressure and temperature change, the properties of all materials change. This has to be considered in a prediction of a blowdown process. 随着温度和压力的变化,所有材料的性质也变化。这在预测一个排放过程中必须加以考虑。The main purpose of a blowdown process is as earlier
stated to maintain integrity of the equipment. The strength properties of the shell are the key factor on that matter. 排放过程的主要目的是如前面讲到的那样,保持设备的完整性。外壳的强度性能是该问题的主要因数。The strength is dependent on the inside pressure as well as the
support forces. 这一强度与内部压力,以及支撑力有关。If the exposing forces produce stress that exceeds the ultimate tensile stress (UTS) in some regions, the integrity of the equipment is no longer maintained. 如果暴露的力产生超过极限拉伸应力(UTS)一定范围的应力,设备就不在能保持完整性。In the design phase of a process plant, these aspects are crucial and must be included as a dimensional factor. For that reason prediction of the blowdown process is essential. Lately some new standards has been introduced to the industry on this matter [3] and [4]. 在工艺设备的设计阶段,这些方面都是很关键的,而且必须作为尺寸因素被包括在内。由于这个原因,排放过程的预测是至关重要的。Z近,一些新的标准已经采用于本行业的这一问题【3,4】。
VessFire [1] and [2] is a multi physics system designed for calculation of this kind of problems. It has been applied for some time in the oil and process industry on many projects. The system satisfies the requirements for predictions outlined in [3] and [4]. It includes all aspects described above including
integrity of the shell. As part of the verification process some experiments where performed. Some of the experiments are presented here. VessFire【1,2】是一种设计用于计算这类问题的多物理系统。它被用于石油和加工行业的很多项目上已有一些时间。该系统满足文献【3】和【4】中概述的预测的要求。它包含了上面描述的所有方面,包括外壳的完整性。作为验证过程的一部分,进行了一些实验。有些实验在这里做了介绍。
EXPERIMENTAL STUDY
实验研究
The purpose of the experiments was to investigate the evaporation process and the heat transfer to the liquid and vapour. In a complex system it is important to reduce unknown parameters as far as possible. 实验的目的是研究蒸发过程和向液体和蒸汽的热传导。在一个复杂系统中,尽可能减少未知参数是很重要的。Exposure from a flame is difficult to control. Flux measurements are point values and not necessarily representative for the average exposure. 暴露于火焰中很难控制。 (热)通量测量是一些点值,而且不一定具有平均暴露的代表性In order to control the heat exposure it was decided to apply an electric heating system. The system and the verification of the system is described in [5], [6] and [8]. 为了控制热暴露,我们决定采用电热系统。该系统和该系统的验证在文献【5】,【6】,【8】中叙述。
The furnace was built inside a supporting tube. Figure 2 shows a general arrangement of the
experimental outfit. 电热炉建在支撑管内。图2示出了该实验装备的总的安排。A 0.05 mm stainless steel foil formed as a tube, 300 mm in diameter, generated the heat. The power supply was based on a 3-phase alternating current system giving 48 Volt output as maximum. The top exposure had a limit of 300 kW. The foil had a surface of about 1 m2, giving a heat flux up to 300 kW/m2. 一根由0.05mm不锈钢箔形成的、直径300mm的管子,产生热。电源是3相的交流系统,Z大提供48V的输出。顶部的暴露机箱为300kW。 不锈钢箔的表面约1m2,能提供高达300kW/m2的热通量。
问题补充:The power input could be continuously regulated from zero to maximum load. Each experiment was started from zero and brought up to the required load within a few seconds. After that the surface temperature of the heating foil was kept constant during the exposure period. Experiments with both dry objects as well as water filled object were performed. 功率输入可以从零到Z大负载连续调节。每一次实验都从零开始,并在几秒钟内升高到所要求的负载。在那以后,加热箔的表面温度就在暴露周期内保持恒定。对干燥物体和充水物体都进行了实验。 In this paper only water filled experiments are presented Figure 2 General arrangements drawing of the experimental furnace including the specimen and its support Figure 3 Illustration of the heating unit. 在本文中,只介绍了充水的实验。图2为包含样本在内的实验炉及其支撑的总安排图。图3为发热单元的示意图。The black part is copper conductors for the foil. The grey part is the heating foil exposing the specimen. The foil is equipped with thermo-elements all marked H, except H5 which is the temperature in a copper ring and H6 which is the temperature between the insulation and the supporting tube. 黑色的部分是用于不锈钢箔的铜导体。灰色的部分是是样本热暴露的发热箔。不锈钢箔配备以热电元件,除了H5外,全都标上H,H5是铜环中的温度,而H6是绝缘和支撑管之间的温度。