Questions tagged [compressors]

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908 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 ...
1 vote
0 answers
21 views

How does compressor ensure that rfgnt exiting the compressor exits at sufficient pressure such as its condensation tmp is always > otsd air temp?

I have very basic knowledge of the refrigerant cycle. I am talking about a Split system Home AC with an air cooled condenser. Assume a basic AC reciprocating or scroll compressor (i.e NOT a variable ...
0 votes
1 answer
71 views

how to interpret plots in ISO 10816-8?

In ISO 10816-8 for reciprocating compressors, there are some plots that show the allowable RMS vs. frequency for every part of a compressor. However, in the text of the standard, it is mentioned that ...
1 vote
1 answer
45 views

Is there a positive displacement compressor that can rival axial compressors in terms of air mass flow to weight ratio?

Is there a positive displacement compressor that can rival axial compressors in terms of air mass flow to weight ratio?
2 votes
3 answers
74 views

Is there a good way to passively dry air in the input of a vacuum pump?

I'm using an a/c compressor as a vacuum pump for small projects that don't need a good vacuum pump, and I'm looking for a way to dry the air in the input, to prevent water from mixing with the oil ...
0 votes
0 answers
22 views

What contributes to the energy cost of multistage compression at high discharge pressures?

I'm getting into hydrogen compression from a theoretical point of view and am looking for a model to describe the energy requirements. I've gathered, that hydrogen is often compressed with piston ...
1 vote
2 answers
27k 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 ...
0 votes
0 answers
33 views

Compressor ratio and addition of battery cooling loop (chiller) in the existing HVAC circuit

Imagine if i want to change my IC car to an electric vehcile, with the obvious addition of battery, how can i use existing HVAC loop to cool the battery using a chiller. HVAC was obviouly desinged ...
0 votes
0 answers
27 views

Retrofitting an old compressor with VFD

For an AC unit, the compressor - GK151PAB - Hermetic type, Permanent split condenser,2 pole, Single phase, Induction motor. This much I know about it. What else do I need to know and how do I find out ...
1 vote
1 answer
58 views

Axial compressor: How does it work that the stator vanes diffuse the flow to build up pressure, but also the flow area reduces?

I'm reading about how the stator vanes are diffusors, which diffuse the air flow in a axial compressor to a larger flow area to build up pressure BUT at the same time the compressor shows its overall ...
1 vote
0 answers
21 views

How can rod load reversal points determine leakage of valves in reciprocating compressors?

One of the common parameters that is monitored in reciprocating compressors is the net rod load. How can they show which valve has leakage? For example, if the suction valve of the crank end (CE) has ...
0 votes
0 answers
45 views

Understanding air compressor CFM, PSI

I need some help in choosing the right air compressor for my airtable and understanding how CFM and PSI can be used to calculate the system. I read standard google links, pressure drop per linear ft, ...
0 votes
3 answers
58 views

Confused about how combustor pressure is lower than compressor exit pressure in turbomachinery?

I understand the compressor exit pressure is the highest pressure in all of the turbomachinery, and the combustor is a constant pressure process, and since the combustor P is lower than compressor ...
0 votes
0 answers
59 views

Why is pressure in a common rail fuel system so much higher than in an air compressor or supercharger?

Superchargers in cars are bulky, expensive, consume considerable amount of engine's power and yet they generate only about 6-9 psi boost. On the other hand, modern common rail diesel engines inject ...
-1 votes
2 answers
2k 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 ...
4 votes
3 answers
133 views

Specific heat at constant volume used in non constant volume processes

I have commonly seen that the work for an isentropic compression is written as: $$ W_{in} = c_{v}(T_1 - T_2) $$ What confuses me is that since it is a compression (volume is changing) why do we use ...
1 vote
4 answers
4k 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 ...
2 votes
3 answers
129 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?
0 votes
1 answer
101 views

What is the correct method to remove or tighten this splined "nut"?

This photo shows the input shaft of an air compressor head. The splined cog-looking disc around the shaft is actually a sort of threaded nut which screws into the larger disc around it. It serves to ...
1 vote
2 answers
117 views

why do centrifugal compressors have curved blades?

Why are centrifugal air compressors built with backward curving blades?
2 votes
1 answer
50 views

Slow Driving an Air Compressor

Do off-the-shelf air compressors have minimum driving speeds, below which they cannot build the necessary pressure? Reciprocating compressors and scroll compressors are available—is there a difference ...
0 votes
1 answer
138 views

Why do high pressure multistage air compressor have different piston diameter sizes? [closed]

I meant like this kind of compressor https://www.bauer-kompressoren.de/fileadmin/_processed_/csm_compressor-block-junior2_b92a76a02e.jpg also would the compressor reach high pressure if the diameter ...
1 vote
0 answers
47 views

Motor part winding start

I have a BITZER compressor type 4GE-23Y-40P, with a part winding start option Nennspannung = nominal voltage = 380-420 Frequ = frequency = 50 Betr. strom = maximal operating current = 43.9 ...
4 votes
0 answers
81 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 ...
-1 votes
3 answers
2k 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 ...
-1 votes
1 answer
47 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 ...
0 votes
0 answers
169 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 ...
1 vote
1 answer
282 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 ...
0 votes
2 answers
84 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 ...
1 vote
1 answer
51 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 ...
1 vote
2 answers
73 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 ...
1 vote
0 answers
21 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 ...
2 votes
1 answer
495 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 ...
4 votes
1 answer
168 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 ...
1 vote
2 answers
345 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 ...
1 vote
2 answers
99 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 ...
1 vote
3 answers
4k 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. ...
0 votes
0 answers
57 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 ...
2 votes
2 answers
776 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-...
0 votes
0 answers
175 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 ...
0 votes
1 answer
31 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 (...
0 votes
2 answers
100 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 ...
7 votes
1 answer
1k 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 ...
2 votes
1 answer
98 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 ...
1 vote
1 answer
633 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-...
-1 votes
2 answers
91 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)...
1 vote
1 answer
176 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 ...
3 votes
1 answer
855 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 ...
0 votes
1 answer
2k 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 ...
1 vote
0 answers
159 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 ...