Questions tagged [compressors]

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28 views

Is there any side effect to soft start an AC motor?

I have a ground to water heat pump for my home heating/cooling (scroll compressor). The 3-phase 15kW-peak motor can be soft started but this option is off by default. I'm aware of all the positive ...
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3answers
34 views

Is it safe to use a 125PSI rated auxiliary air tank with a 150PSI air compressor?

I have a small, 5 gallon, pancake compressor which has a maximum 150PSI rating. Unfortunately, it doesn't have the air capacity to power the demands of an HVLP paint sprayer or a die grinder without ...
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0answers
15 views

Calculating (transient) rate of cycles of practical thermodynamic engines (turbojet, multi-cylinder car engines etc..)

I already asked this on Physics Stackexchange but to no avail. Thought this forum is a better place to ask this. I tried to make a plan for a turbojet engine with my physics knowledge and I'm stumped ...
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1answer
36 views

How to decrease Nitrogen gas consumption in Iron & Steel Plant? [closed]

I need to decrease nitrogen gas consumption in iron & steel plant. Currently it's not possible to measure every dot from steel mill to determine real usage so they use what air separation unit ...
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1answer
24 views

Why do centrifugal compressors have a higher compression ratio per stage than axial compressors?

It is common for centrifugal compressors to have a pressure ratio of one stage of 3, while axial compressors often have compression ratio per stage of around 1.25. What is the source of that ...
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34 views

Work done by compressor to fill a tank

A reciprocating air compressor is used to fill rapidly a $3m^3$ tank at $30°c$ and $1\ bar$. The filing process is governed by $pv^{1.4}=constant$. The effects of kinetic energy may be neglected. The ...
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2answers
26 views

How do stators in axial compressors work?

How do the stators in axial compressors convert kinetic energy to pressure? Is this equivalent to a water hammer?
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2answers
61 views

Regarding design of a compressed air delivery system based on a screw air compressor

I want to select a screw compressor for my application wherein I need a pressure of about 18 psig, and 300 cfm at the aforementioned pressure. The compressors I'm finding suitable for the system have ...
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1answer
19 views

Do stators in axial flow compressors have airfoil geometry?

In axial flow compressors the role of a stator is to gradually change the direction of flow to exchange some of the kinetic energy of the flow into pressure. Therefore it stands to reason that they do ...
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2answers
70 views

why not put the compressor right next to the evaporator?

the cold line from evaporator to compressor will gain tons of heat on a super hot day even with insulation. if they put the compressor right outside the evaporator, both of the long lines will be hot ...
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0answers
17 views

Ignoring Mechanical Material Properties and Design Implications, in a Compressor, does the Thermal Density of the Blades Affect Efficiency?

Consider an ideal adiabatic compressor, ignoring the remainder of the thermodynamic cycle. In this case, the heat flow q into and out of the compressor itself is zero, by definition of adiabatic ...
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1answer
204 views

What is diffusion in the context of compressor?

When studying about the axial compressor, I came across the term 'diffusion' being used to explain the conversion of kinetic energy to pressure, also terms like 'diffusion factor'. What is being ...
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2answers
37 views

Is there a way to calculate mass flow rate of an axial compressor?

Is there a rule of a thumb equation for the mass flow rate of a stationary axial compressor at sea level, using intake area and RPM? Or do other factors like blade geometry make too much of a ...
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2answers
31 views

Compressing gas with liquid

This question, in short, is: Can a gas be compressed with high pressure liquid? As a scenario, imagine a tank full of atmospheric gas at STP. Could something like a pressure washer pump (in this case ...
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0answers
27 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
208 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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0answers
50 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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0answers
96 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 ...
4
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1answer
145 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
29 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
76 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
14k 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
82 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
242 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
1k 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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0answers
95 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
94 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
56 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
86 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
29 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
65 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
36 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
117 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
229 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
752 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
3k 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
115 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
2k 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
642 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, ...
3
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1answer
664 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
32k 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
570 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
295 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
222 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 ...
2
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1answer
70 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
58 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
932 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
1k 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
663 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 ...