Heat extraction

The success of the process results from the fact that nowhere inside the furnace is heat extracted from the copper-saturated blast furnace buUion through a soUd surface. The problem of accretion formation (metal buUd-up), which has plagued many other attempts to estabUsh a copper dtossing operation of this type, does not arise. In the cooling launder, lead-rich matte and slag accumulate on the water-cooled plates, but these ate designed so that when they ate lifted from the buUion stream, the dross cracks off and is swept into the furnace via the cooled lead pot. 

H values are proportional to the heat-extracting capacity of the medium. 

Core damage can result most likely from heat imbalance. Figure 6.3-3 is an example from the Indian Point PRA that uses heat imbalance to approach completeness. This diagram shows that cote damage may result from either a loss of cooling or excess power (or both). The direct causes of insufficient heat removal may be loss of flow, makeup water, steam flow, or heat extraction by the turbine. Indirect causes are reactor trip or steam line break inside or outside of containment. Cau.ses of excess power production are rod withdrawal, boron removal, and cold water injection. 

Kehlhofer explains that the pre-heating loop must be designed so that the heat extracted is. sufficient to raise the temperature of the feed water flow from condenser temperature T to Ta (see Fig. 7.6). The available heat increases with live steam pressure Ipf), for selected 7 b(= Ta) and given gas turbine conditions, but the heat required to preheat the feed water is set by (Ta — T. ). The live steam pressure is thus determined from the heat balance in the pre-heater if the heating of the feed water by bled steam is to be avoided but the optimum (low) live steam pressure may not be achievable because of the requirement. set by this heat balance. 

Porous Media Any solid material through which gas can flow, and that affords some measure of heat extractive capability and flame quenching by cooling. 

This is used when (1) the room needs heating instead of cooling or (2) for reheat as described above. It is vital in close control systems that its capacity is sufficient to maintain room temperature under these conditions, otherwise the system may fall into a loop, with the controls continuing to see high rh due to temperature. Using only part of the cooling coil for dehumidification will alleviate this situation. A heater capacity of the sensible heat extracted during dehumidification plus half the peak winter fabric loss is recommended where the room load could be nil in winter such as a start-up situation. 

The unit of heat is the watt. However, the imperial unit should be understood, as it will still be met, particularly outside Europe. The ton of refrigeration is derived from an ability to remove sufficient heat from a short ton (2000 lbs) of water at 32°F to turn it to ice at the same temperature in the course of 24 hours. This amounts to a heat extraction rate of 3.517kW. 

The rate of heat extraction, i.e. the product cooling load, will he Q = H/1 where t = the time available for cooling. 

With induction units, latent heat extraction can usually he handled hy the primary air and they run with dry coils. Some systems have heen installed having high latent loads which remove condensate at the coil. 

In modem, packaged horizontal FT boilers, the furnace is the most important heat-transfer component, typically providing 50 to 60% of the total heat transfer from only 30% or so of the total available heating surfaces. This level of heat transfer, coupled with the additional heat extraction obtained by the various multiple-pass designs (four passes is a practical maximum) provide efficiencies of 80 to 83% GCV. As a result, there generally is little additional benefit to be obtained from the use of economizers or air heaters, especially when using oil-fired boilers, which can operate at up to a 3% or so higher efficiency level compared to gas-fired units. 

Also, many operators commonly generate electrical power as a primary function via gas turbine or diesel engines, and then as a secondary function use heat extracted from the cooling jackets and flue gases to generate steam in a WH boiler or a HR boiler. 

In all observed processes, only a fraction of the heat extracted from a heat reservoir can be converted into work, with the remainder returned to a lower temperature reservoir. 

Reactor electrical heat input(l) Coil/jacket heat balance Condenser heat extract rate (1) Reactor heat loss... 

Alternative approaches consist in heat extraction by means of thermal analysis, thermal volatilisation and (laser) desorption techniques, or pyrolysis. In most cases mass spectrometric detection modes are used. Early MS work has focused on thermal desorption of the additives from the bulk polymer, followed by electron impact ionisation (El) [98,100], Cl [100,107] and field ionisation (FI) [100]. These methods are limited in that the polymer additives must be both stable and volatile at the higher temperatures, which is not always the case since many additives are thermally labile. More recently, soft ionisation methods have been applied to the analysis of additives from bulk polymeric material. These ionisation methods include FAB [100] and LD [97,108], which may provide qualitative information with minimal sample pretreatment. A comparison with FAB [97] has shown that LD Fourier transform ion cyclotron resonance (LD-FTTCR) is superior for polymer additive identification by giving less molecular ion fragmentation. While PyGC-MS is a much-used tool for the analysis of rubber compounds (both for the characterisation of the polymer and additives), as shown in Section 2.2, its usefulness for the in situ in-polymer additive analysis is equally acknowledged. 

While most polymer/additive analysis procedures are based on solvent or heat extraction, dissolution/precipita-tion, digestions or nondestructive techniques generally suitable for various additive classes and polymer matrices, a few class-selective procedures have been described which are based on specific chemical reactions. These wet chemical techniques are to be considered as isolated cases with great specificity. 

Liquid (solvent) extraction is not the only way of sample preparation, but stands along with various forms of heat extraction (headspace, thermal desorption, pyrolysis, etc.) and with laser desorption techniques. 

As to Irgafos 168 the reader is advised to notice the results of a round-robin involving PP/(Irganox 1076, Irgafos 168) [209a], Ultrasonication at room temperature with anhydrous n-hexane or acetone is a suitable soft extraction mode for the determination of aromatic phosphites and phosphonites, such as Ultranox 626 and Sandostab P-EPQ, which easily degrade in heating extraction procedures [210]. 

This chapter deals mainly with (multi)hyphenated techniques comprising wet sample preparation steps (e.g. SFE, SPE) and/or separation techniques (GC, SFC, HPLC, SEC, TLC, CE). Other hyphenated techniques involve thermal-spectroscopic and gas or heat extraction methods (TG, TD, HS, Py, LD, etc.). Also, spectroscopic couplings (e.g. LIBS-LIF) are of interest. Hyphenation of UV spectroscopy and mass spectrometry forms the family of laser mass-spectrometric (LAMS) methods, such as REMPI-ToFMS and MALDI-ToFMS. In REMPI-ToFMS the connecting element between UV spectroscopy and mass spectrometry is laser-induced REMPI ionisation. An intermediate state of the molecule of interest is selectively excited by absorption of a laser photon (the wavelength of a tuneable laser is set in resonance with the transition). The excited molecules are subsequently ionised by absorption of an additional laser photon. Therefore the ionisation selectivity is introduced by the resonance absorption of the first photon, i.e. by UV spectroscopy. However, conventional UV spectra of polyatomic molecules exhibit relatively broad and continuous spectral features, allowing only a medium selectivity. Supersonic jet cooling of the sample molecules (to 5-50 K) reduces the line width of their... 

Recovery procedures have traditionally involved some form of solvent, gas or heat extraction from the bulk sample matrix. Some of these lend themselves to precolumn hyphenation (e.g. SFE, TD, Py, HS), as opposed to others (e.g. Soxhlet, ultrasonics). Extraction of additives should not be considered as an isolated step, because it may strongly influence the subsequent chromatographic separation. The success of an analysis may very often depend more on the extraction procedure than on the chromatographic separation. In hyphenation there should be compatibility between the sample preparation and subsequent chromatographic analysis. 

Heat extracted from the gas in cooling from 800 to 200° C, for each component ... 

The benzene strip or extract solutions are evaporated nearly to dryness in 500-ml. standard-taper Erlenmeyer flasks on 3 units of a 6-unit variable heat extraction apparatus hot plate (see Figure 1). Evaporation is hastened by directing a jet of air at the surface of the benzene, gentle enough to avoid spattering when maintained 0.5 inch above the surface of the liquid. The benzene vapors are removed through a manifold connected to the house vacuum. On this apparatus 250 ml. of sample can be reduced to a volume of about 5 ml. in 10 minutes. 

An advantage over the line source method and other parameter estimation techniques is that the estimate can be made directly on the measured return temperature. Using the derived average heat extraction or injection rate may... 

Figure 55. Geothermal response test with combined heat extraction/heat injection and different energy levels, shown are the borehole heat exchanger flow and return temperatures and the calculated heat flux. Borehole flow rate is not shown in the graph...

The test commences with a heat extraction of about 1 kW (duration 45 h), subsequently this extraction rate was increased to 1.35 kW. After a total time of 60 h, a short recovery period (10 h) was allowed. During this period the heat pump was reversed and started storing heat in the buffer tank. Subsequently a heat injection of about 1 kW was started, after which there is a transient power injection with a maximum power injection rate of about 3.4 kW. The experiment settings have to be adjusted manually, therefore some control problems are obvious in the graph. For instance, when changing to... 

Plotting the errors for all individual data points (Figure 56) for the different calibration runs it is clear that largest errors are associated with periods of transient heat flux. Moreover, errors during the period with heat extraction (1—40 h and 1-80 h), increase with time. 

In this paper we present for the first time a test that combines heat extraction and heat injection pulses in one experiment. It is expected that differences in the ground thermal conductivity, when different data windows are used to obtain an estimate, can be related to advection and convection of ground water. The real ground conductivity should be derived from the experimental data where the response is close to or lower than the natural ground temperature, minimizing effects of advection and convection. First results, for a case of no ground water flow, show that estimates of ground thermal conductivity are very comparable for the different data windows. 

Heat extraction from the bedrock by a heat pump system is an environmental friendly heating method where 70% of the heat is taken from the ground. This... 

Figure 57. Outline of borehole system for heat extraction...

When the brine has given its heat to the heat pump it is a few degrees colder on the way back to the rock. The heat extraction from the borehole lowers the ground temperature, but after a few years this temperature drop will reach to a point, a steady state, where it will be restored during the summers. 

If only one of these problems occurs it will not be a big problem, but if more than one problem occurs it will lead to under dimensioning and freezing will take place. The easiest and most common ways to solve the problem is either to drill the borehole deeper, drill a new borehole or to reduce the heat extraction. To reduce the heat extraction an additional heater must be used. 

To get a better understanding of the problem with freezing a temperature indicator could be placed along the collectors to monitor the temperature during heat extraction, as shown in Figure 67. 

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