The method for determining heat losses machines and devices

 

(57) Abstract:

Usage: for machines and devices that work with a given load, the heat which proceeds according to the laws of homogeneous heat of the body. The inventive method is based on the direct determination of loss on actual progress of the heating or cooling of machines and devices. Heat loss is determined from the expression given in the description.

The invention relates to methods of determining heat losses (efficiency) machines and devices that work with a given load, and the levels of overheating, the heat which proceeds according to the laws of homogeneous heat of the body. The invention can be used in bench testing of engines, gearboxes, etc. of machines and mechanisms and in the course of their operation.

Known methods of determining the efficiency of the gears based on the measurement of power lost to heat circulating lubrication, power lost due to heat exchange with the ambient air, and the power supplied to the gear [1]

When using this method, measured values of the above capacities and, using known expression, get index (KtS) characterizing the heat is conducted indirect, because it is based on measurements in idle mode, and applies to modes real loads;

2) the method is applicable when the transmission is in thermal equilibrium mode, which requires at least several hours of long-term operation and maintenance of stable parameters of the experiment: power, ambient temperature, etc.

The aim of the invention is to provide a method for measuring losses of machines and devices of any type, based on the direct determination of loss on actual progress of the heating (cooling) of these machines and devices for the cases when the process of heating (cooling) occurs according to the laws, closest to the laws of the heating (cooling) of a homogeneous body.

This goal is achieved by the fact that thermal losses (efficiency) when working with a given load in the steady-state thermal conditions with established superheat (y) relative to the environment is defined as the productyon the relationship of the values of the heat capacity C of machines and devices, as defined by the design parameters, to a constant heat time T, to determine which, firstly, through successive equal time intervals to determine the current values of the lines from the previous and the time constant of heating is determined from the expression:

< / BR>
where t successive equal intervals of time of heating, after which produce measurements;

n-2superheat set at the initial moment of measurement;

n-1is overheating after a time t;

nis overheating after a time 2t, and the value ofydetermined from the expression:

< / BR>
whereyestablished superheat;

l the base of the natural logarithm.

The determination of the values of overheating and increments of these values is in the process of heating (cooling) of machines and devices, but because the method makes it possible to obtain the value of losses on actual progress of the heating as a result of their operation.

The essence of the method lies in the fact that the process of heating machines and devices running under the laws of the homogeneous heat of the body, characterized by the constancy of relations incrementsn[n-n-1] Kn-1[n-1-n-2] for two adjacent equal time intervals.

To determine the constant T in the heating process to produce, for example, using thermocouples to measure the levels of overheating through posledovatelnuju (finite difference) of two adjacent successive time intervalsn-1=n-1-n-2n=n-n-1and so on, where 0, 1, 2, 3, respectively, first, second, third, etc. moments of measurement.

The relation is over heating process constant.

From the expression defined constant, T is the heating time, and from the expression superheat.

The heat capacity of machines and devices C is defined as the sum of the heat capacities of its constituent parts.

Then the heat loss (efficiency) when working with a given load machines and devices are determined from the known expressions:

and

The method for determining heat losses machines and devices operating with a given load in the steady-state thermal conditions with established superheat relatively okrujayushaya environment, consisting in the measurement of parameters that calculate heat loss, characterized in that in the heating process through successive equal intervals of time measured current values overheating and increment these values for each successive time interval relative to the previous and heat loss Rmis determined from the expression

< / BR>
where C is the heat capacity of machines and devices;

T is the time constant at which the quiet measure;

n-2- superheat set at the initial moment of measurement;

n-1- is overheating after a time t;

n- is overheating after a time 2t;

y- established superheat determined from the dependence of

< / BR>
where e is the base of natural logarithm.

 

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