Upward ventilation

Drain Opener. This reaction MUST be performed in an area of adequate upward ventilation, or at feast with the air flowing away from you. 

Air iniakes positioned to ensure draft-free conditions in the occupied zone FIGURE 9.26 Upward ventilation, large fiall. 

Research on airflow catastrophic of side branches induced by gas pressure in upward ventilation... 

School of Resource cmd Safety Engineering, State Key Laboratory of Coal Resources and Mine Safety, Beijing, China University of Mining Research on Airflow Catastrophic of Side Branches Induced by Gas Pressure in Upward Ventilation and Technology, Beijing, China... 

ABSTRACT In order to analyze the law of airflow catastrophic of side branches induced by gas pressure in upward ventilation after dynamic of outburst disappearing, one dimensional unsteady-state flow momentum equation of gas flow is established. Combined with circuit airflow pressure balance equation, this equation is used in static and dynamic analysis on airflow catastrophic of side branches induced by gas pressure in upward ventilation. The research results show that gas pressure is produced in upward ventilated roadway when gas flowed by when the gas pressure is great enough, the air flow in side branches reverses. Whether the air flow in side branches reverse is affected by their own length and initial velocity. In order to prevent the air flow reversal in the side branches, it is necessary keep the fan normal operating, and avoids adding resistance in external system. The research results may be of important theoretical and practical significance for outburst accident rescue as well as effective prevention of the occurrence of secondary accidents. 

When gas pressure produced in upward ventilated roadways, its direction is the same as fan pressure, which is positive for the fan when gas pressure produced in downward ventilation roadways, its direction is opposite to fan pressure, which is negative for the fan. 

THEORETCAL ANALYSIS AIRELOW REVERSAL OF SIDE BRANCHES INDUCED BY GAS PRESSURE IN UPWARD VENTILATION... 

When outburst occurs in mine, airflow catastrophic will occur in intake airways connected with the source of outburst because of the great impact force produced by gas flow transiently released and of the gas pressure after the dynamic of outburst disappears, of which the most typical is airflow reverse of side branches. Therefore, this paper will use one dimensional unsteady-state flow momentum equation established above to analyze law of airflow reversalof side branches induced by gas pressure when upward ventilation airflow catastrophic occuring. 

After outburst occurs, if cannot be controlled timely, great gas pressure will be produced in upward ventilated airways methane flowing by. en hi is great enough, airflow in side branch b will reverse. 

When outburst occurs, airflow reversal of side branches in upward ventilation is related with the length and original velocity of the branch. 

Current mixing-type air distribution methods typically consider ventilation of the occupied zone with jets intercepting its upper boundary (e.g.. Fig. 7.6l2, c). Also, the occupied zone can be ventilated by the reverse flow produced as the supply jet degrades above the occupied zone level (Fig. 7.6h]. Mixing-type air distribution methods include air supply with jets projected vertically downward, inclined jets, jets directed vertically upward, and horizontal jets along room surfaces. 

If the supply jet is inclined upward, while situated at the front of the table, its function could be similar to an air curtain in an opening. However, the inclination from the horizontal for the jet is usually very slight, since angles above 3 to 10 degrees sharply deteriorate the function of the ventilation system. If the jet is directed vertically, it should be placed along the back wall, blowing upward. 

If the flow is isothermal, there is no need to solve for the temperature equation (Eq. (11.6)). In this case the last term in Eq. (11.5) is also dropped. If, however, the thermal comfort is simulated, then the temperature equation must be solved. In ventilation the temperature variations are normally small, which means that it is sufficient to account for density variation only in the gravitation term (the last term in Eq. (11.5)). The gravitation term acts in the vertical direction, and in Eq. (11.5) it is assumed that the xj coordinate is directed vertically upward. denotes a reference temperature, which should be constant. It does not influence the predicted results, except that the pressure level is changed. It could, however, affect convergence rate (i.e., increase the number of required iterations required to reach a converged solution), and it should be chosen to a reasonable value, such as the inlet temperature. 

Ignition prevention by an automatic disconnection of the battery in case of an accident, separation of fuel supply lines and electrical systems, and design of proper systems for both active and passive ventilation, such as openings to allow hydrogen to escape upward. 

Fig. 15. Relationship between the alfentanil plasma concentrations and the probability of needing naloxone to restore adequate spontaneous ventilation. The diagram at the upper part shows the alfentanil plasma concentrations of the patients who required naloxone (upward deflection) or did not require naloxone (downward deflection). The plasma concentration-effect curve for this clinical endpoint (lower part) was defined from the quantal data shown in the upper diagram using logistic regression. Bars indicate SE of C5o%. (From Ausems ME, Hug CC, Stanski DR, Burm AGE. Plasma concentrations of alfentanil required to supplement nitrous oxide anaesthesia for general surgery. Anaesthesiology 1986 65 362-73, reproduced by permission.)...

The vapours are drawn off the nitrators via a ventilator and flow upwards into a tower where they are sprayed with water, and recovered as 20% nitric acid. 

The beauty of magnetic bombs is that the explosive force is delivered principally in one direction, upward, with little side blast Its effect is akin to sitting on a claymore mine. I ve examined photographs of two cars involved in these attacks, and the only real damage, apart from a hole in the floor, consisted of broken windows and a badly ventilated roof. 

Carbon Monoxide is scarcely a normal constituent of fresh air, although it occurs in the minutest traces m the air of towns and of volcanic districts. It also occurs m railway tunnels 3 and even in well-ventilated coal mines to the extent of 0-002 to 0-00-1 per cent.4 It is a most dangerous gas, 0-48 per cent, being fatal to man 5 in a short time. Even 0-2 per eent. may prove fatal if breathed for a long time. Headaches and other unpleasant symptoms are produced hv concentrations ranging from 0-03 upwards. 

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