If the voltmeter is connected in parallel with the consumer and power supply, whose voltage is measured by the voltmeter

If the voltmeter is connected in parallel with the consumer and power supply, whose voltage is measured by the voltmeter

Is the voltage of another consumer in series with the consumer

There are two electrical appliances in the circuit, each with a voltmeter in parallel in one of the electrical appliances. When one of the electrical appliances is short circuited, what is the change of voltage indication

"There are two consumers in the circuit, each with a voltmeter in parallel in one of them"
It shows that the two consumers are in series
"When one of the appliances is short circuited"
Equivalent to the two ends of the appliance, connected with a wire
Therefore, the reading of voltmeter of short circuit appliance becomes smaller and basically zero
The voltmeter of another electric appliance is directly connected to both ends of the power supply, and the reading becomes larger, which is basically equal to the power supply voltage

The battery can convert chemical energy into electrical energy. How can it be converted into chemical energy when the electrical energy from the consumer returns to the battery?

Electric energy will not be converted into chemical energy. Otherwise, the energy will not be used up
In fact, power is consumed in the circuit, not "back to battery."
PS：
When we charge a rechargeable battery, it is the electrical energy that is converted into the chemical energy of the battery