Questions tagged [compressors]

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11 views

In a throttling process do we consider static pressure or stagnation pressure and is there a reverse throttling process?

In a throttling process, the 'pressures' decreases whereas the enthalpy and so the 'temperature' remains constant. Are these pressures and temperatures static values or the stagnation values? I am ...
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1answer
32 views

Why stagnation temperature doesn't change in stator

I was going through a review of rotary compressor and i understood that the stagnation pressure and stagnation temperature both change in the rotor stage (as energy is being added).I also read that in ...
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39 views

Force of Jet from Air Compressor

I want to use a compressor to create a jet of air. At discharge from compressor how much CFM (Cubic Feet per Minute) are enough to create a force that can turn a heavy object (say 40 kg) at 3 rev per ...
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24 views

Could I define an isothermal efficiency?

There's an adiabatic efficiency because real processes can't be adiabatic. I want an isothermal compression (yes, I know an adiabatic compression consumes less work, but my pressure differential is ...
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1answer
117 views

Is Scrooge's giant glass dome feasible in real life?

In an Uncle Scrooge (or Scrooge McDuck, not sure of the translation here) comic named "Treasure Under Glass", Scrooge orders a giant glass dome to be manufactured in order to aid his endeavours ...
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1answer
21 views

Pressure delivered to an object under a pneumatic press

I'm hoping some kind person can tell me if I have this right or not. I swear this isn't a homework problem. I'll be using a heated pneumatic press to heat seal lidding to plastic containers (...
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2answers
66 views

If the turbine drives the compressor, then what limits the engine speed?

My understanding of a typical jet engine is that when running, the turbine extracts energy from the hot exhaust gases. This drives the turbine, which is coupled to the compressor at the front of the ...
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2answers
6k views

Define Free Air Delivery for an air compressor

Free Air Delivery (FAD) is a common measure of the capacity of an air compressor. I have a question that comes at the end here. My question is a little different from what you might be expecting. So ...
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1answer
54 views

Recommended compressed air source and location for separate air compression system

I am investigating what would be the most appropriate compressed air source (fan/blower/compressor) for designing a separate air compressor system. The information is as follows: the compressed air ...
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1answer
110 views

Force to compress flexible elastic tubing

How would one work out the force required to compress flat, using a flat bar on top pressing down, a thick walled (15mm OD 10mm ID) piece of flexible plastic (PVC) tubing i.e. so reducing the x-...
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1answer
640 views

What is the reason for a reduction in entropy in a compressor

I was under the impression that the entropy reduction in a system only works with either mass or heat transfer. While I was researching intercooling of compressors I stumbled across a peculiar ...
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77 views

Adjusting the pressure of the condenser and the evaporator

The picture below shows a refrigeration unit I was reading the operation manual of this unit. It is written that the pressure of the condenser is controlled by the water flow rate. Reducing water ...
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1answer
64 views

can we run rotary compressor of Air conditioner with different frequency level?

I am working on split type AC compressor. I actually want to know, if i changed the frequency of the compressor to run on different power level, will it affect the life of the compressor. My actual ...
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1answer
52 views

What will remain constant during the circulation of working substance in a refrigerating machine? [closed]

For Example, the pressure of evaporator can be changed, also the pressure of condenser and many more parameters. What is that parameter which remain constant while others keep changing ?
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2answers
73 views

Good or bad (AC Split compressor input with cold freon)

Hermetic Compressor is used by split Air Conditioning unit. The compressor compressed freon gas coming from indoor unit. The gas is usually quite cold (about 2 deg.C lower than inside room temperature)...
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1answer
27 views

Compression and check valves

Pressure pumps are used to apply pressure to a system. What would happen if someone attempted to fill, for example, a bicycle tire (with a check valve) to 2 ATM of pressure using a pressure pump that ...
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1answer
56 views

Axial compressor - change of temperature not proportional to number of blades and their geometrical properties?

I'm learning theory of axial compressors for my summer internship and I find some of the equations puzzling, although I do understand the way they were derived. The equation bellow is for temperature ...
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1answer
31 views

Help me find a paper/textbook on axial compressor in turboshaft engine [closed]

I'm trying to calculate the values of pressure, temp, speed and density of air going through an axial compressor (12-stage) a helicopter. I've read a few bachelors' thesis and papers but wasn't able ...
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2answers
99 views

What is a good non-combustible oil to be used in air compression regenerative braking/energy storage system for cars, buses, and trucks?

An important energy storage method that is being given very little consideration is gas compression. The kinetic energy of the vehicle can drive an air pump or compressor that would compress air into ...
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1answer
2k views

Air Conditioners: Compressor Explosions?

In this piece of news it is said that an Engineer and Blogger named Utpal Chakrabarti has died after explosion of air conditioner compressor. My question is, how dangerous air conditioners are? Which ...
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4answers
152 views

What type of air blower/compressor to use?

I need a way to move air which is somewhere in between a compressor and a fan: something along the lines of 20-40 cfm at 2-3 psi (500-1000 liters/minute at 10-20 kPa). Typical small compressors (of ...
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1answer
512 views

Is a 3 Hz beat frequency from my neighbor's HVAC a sign of a malfunction?

I'm being annoyed by a pulsating hum which comes from my neighbor's HVAC system. I read up a little on the design of HVAC systems and I came to a tentative conclusion that what I'm hearing is a ...
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3answers
2k views

Could an air compressor be used to compress steam?

Could an air compressor be used to compress steam? What would be practical problems if any? Say I have saturated steam at 1 barg and I need to compress it to 2 barg. In theory could I just pipe to ...
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1answer
103 views

Is the efficiency of a reciprocating air compressor constant for all allowable values of Pressure?

Efficiency = Actual Mass displaced by the compressor divided by the theoretical mass displaced. If we continuously increase the pressure in the compressor tank, will the efficiency stay roughly ...
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3answers
1k views

What is the difference between a piston and a plunger compressor/pump?

My research has found a Quora link and another source giving two different, albeit not contrasting, definitions. Also, as far as I have seen, looking up "plunger compressor" also refers me to pumps. ...
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4answers
395 views

How does a stator convert velocity into pressure?

I'm looking for, hopefully, a qualitative answer to how a compressor increases pressure. I understand the equations that predict this result but I can't picture it in my head. A rotor spins, ...
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1answer
549 views

Volumetric efficiency versus pressure ratio for rotary compressor

I am trying to plot the efficiency graph of a rotary compressor. I already calculated the volumetric & polytropic efficiencies and the graph versus evaporating temperature is as follows: Now i ...
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2answers
25k views

How does loading and unloading work in an air compressor?

I am looking at an ammonia refrigeration unit and trying to understand how loading and unloading solenoid valves work? and also how to modulate the compressor motor over a period of time.
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2answers
439 views

Why no hydraulic piston gas compressors?

I've been looking at solutions to compress gases and getting stunned by the cost and maintenance requirements of existing systems to fill cylinders (whether for SCBA or chemical storage) to 2000-...
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2answers
250 views

What are these bent shapes on this elbow in a compressor suction pipe?

See here are the shapes which are made on the suction head of compressor, What are these, and why are they on the suction head pipe?
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1answer
187 views

Air tool to compressor backflow

As I was reorganizing my air tool arsenal, a theoretical question popped in my mind I'd like to know the answer to. In designing air flow between an air compressor and a tool (such as a nailer or an ...
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1answer
64 views

Lightweight Air Compressor

I need a small air compressor for a robotics application. I currently have one of those 12V tire inflators (200 psi, 1 CFM or so) that is sized well for this purpose (sample image below). However, in ...
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0answers
55 views

How are small refrigerator compressors started?

Small refrigerator compressors in the US generally all have exactly the same design and I am trying to understand their starting mechanism better. How exactly does it work? What I generally ...
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2answers
713 views

How can flow in a centrifugal compressor at fixed conditions vary?

Consider a centrifugal compressor. The compressor map usually plots the adiabatic head vs volumetric inlet flow for rated conditions of pressure, molecular weight and temperature at a given speed. But ...
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1answer
854 views

Finding the mass in the tank of an air compressor from gage pressure

I am solving the following problem: The tank of an air compressor has a volume of 3 cubic feet and is filled with air at a temperature of 40 °F. If a gauge on the tank reads 150 psig, what is ...
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2answers
519 views

Gigapascal pressures in a small package

How small/compact can a pump or other mechanism be, that would allow compressing gas (or liquid) to pressures of excess of 10GPa, continuously? Throughput may be minuscule, of order of milligrams per ...
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2answers
804 views

How does a compressor know to lower condensing pressure in chiller?

I am working on an indirect ammonia chiller that is used to cool the ice in an arena. The system consists of 3 reciprocating compressors, an evaporative condenser with a vfd on the fan, a float ...
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2answers
2k views

Typical power consumption of large compressor

This one should be easy to answer by looking at the thermodynamics, but I find it not to be. Say we have a natural gas stream, ~700 N∙m3/h, that we want to compress from 16 bar to 250 bar. What will ...