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Envision Engineering & Skill Development, Monesware Road, Zigatola, Dhanmondi, Dhaka (2026)

20/11/2025

RO Membranes and Module Types
A. Spiral Wound (the industry standard)
• Most common in desalination and industrial plants.
• Compact, efficient, and easy to replace.
• Limitation: prone to fouling with high solids or viscous feed.

B. Hollow Fiber (the “fine filter”)
• Excellent for low-turbidity feeds.
• Offers high surface area in small volume.
• However, fragile and sensitive to pressure shocks.

C. Tubular (the fouling fighter)
• Designed for high-solid or oily wastewater.
• Easy to clean (CIP friendly).
• But larger footprint and higher energy use.

D. Plate-and-Frame (The flexible option)
• Ideal for small systems or testing setups.
• Allows easy membrane replacement and inspection.
• Not suitable for large-scale operations.

19/11/2025

Probable research fields in thermofluid include renewable energy technologies (such as fuel cells, solar, and wind power), aerospace and automotive applications (including engine design and aerodynamics), and micro- and nano-scale systems (like microfluidics for bio-medical applications). Other areas involve biofluids, combustion, heat transfer in buildings, and advanced computational modeling.

Energy and Sustainability

Renewable energy systems: Researching and designing technologies for solar, wind, and wave energy capture, as well as investigating hydrogen production and storage.

Energy conversion: Developing and optimizing fuel cells, batteries, and electrolysis systems for green energy.

Sustainable power: Creating smart grid technologies to improve the efficiency of energy storage and delivery.

Energy efficiency: Improving energy efficiency in buildings, industrial processes, and cooling systems for electronics and data centers.

Aerospace and Automotive

Aerodynamics: Researching areas like aerodynamic shape optimization and hypersonic flows.

Engines and propulsion: Improving air-breathing engines, understanding combustion processes, and developing advanced cooling techniques.

Vehicle efficiency: Analyzing thermal systems in automotive applications and improving designs for fuel efficiency.

Advanced and Micro-scale Systems

Micro- and nano-fluidics: Investigating fluid behavior at the micro- and nano-scale for applications in areas like medicine and materials science.

Biofluidics: Using computational fluid dynamics to study biological systems, such as cardiovascular flows and colloidal flows.

Combustion and reacting flows: Developing chemical models, using laser diagnostics, and studying soot formation in reacting flows.

Other Research Areas

Advanced computational methods: Developing new computational and numerical methods for simulating complex thermofluid phenomena.

Experimental techniques: Advancing measurement and diagnostic techniques for studying fluid and thermal systems.

Heat and mass transfer: Studying fundamental heat transfer mechanisms, with applications in manufacturing, and exploring phase change for cooling and energy storage.

18/11/2025

A screw type compressor shows over-temperature primarily due to poor cooling caused by inadequate ventilation, high ambient temperatures, or clogged oil/air filters. Other reasons include insufficient or incorrect oil levels/viscosity, a malfunctioning thermal valve, or a faulty aftercooler.

18/11/2025

Cooling and ventilation issues

Poor ventilation: The compressor is in a space with inadequate airflow, causing hot air to recirculate instead of being exhausted.

High ambient temperature: The surrounding air is too hot for the compressor's cooling system to be effective.

Dirty or clogged aftercooler/heat exchanger: Dust and debris block the cooling fins, reducing its ability to dissipate heat.

Restricted airflow: Insufficient space around the compressor unit itself can impede proper airflow.

Oil and lubrication problems

Low oil level: There isn't enough oil to properly cool and lubricate the internal components.

Incorrect oil: Using the wrong type of oil that doesn't have the correct viscosity and heat properties can cause overheating.

Clogged oil filter: A blocked filter restricts oil flow, leading to inadequate lubrication and cooling.

Degraded oil: Oil that has broken down over time can lose its effectiveness.

Other mechanical and operational factors

Defective thermal valve: If this valve is stuck, it can prevent oil from reaching the oil cooler.

Clogged oil separator: A clogged separator can restrict oil flow.

Mechanical wear: High noise or vibration can signal internal wear that causes excess heat.

15/11/2025

The process of air cooling through a water-soaked tube system, where hot air enters one side of a series of tubes that are continuously soaked by running water from above. As the hot air passes through the tubes, the water absorbs heat from the air, effectively cooling it. The cooled air then exits from the opposite side of the tubes, while the water, having absorbed the heat, is collected and passed through the tubes at the bottom for recirculation or disposal. This system demonstrates an efficient natural cooling method leveraging ev***rative cooling principles, where heat transfer occurs between the hot air and the water-soaked surfaces, resulting in a consistent flow of cool air.

15/11/2025

Understanding

Strainer vs Filter - Key Difference

Explained

In industrial systems, power plants, and process industries, choosing between a strainer and a filter plays a crucial role in maintaining equipment reliability, ensuring process efficiency, and achieving the desired fluid quality.

1. What is a Strainer?

A strainer is a coarse filtration device designed to remove large solid particles such as rust, weld slag, or sand from a liquid or gas stream. Its primary purpose is to protect downstream equipment like pumps, valves, and heat exchangers from damage.

Key Features:

Utilizes a mesh or perforated screen (commonly stainless steel) for particles typically above 40 μm.

Low pressure drop during operation.

Easy to clean and reusable by removing or back-flushing the screen.

Common configurations: Y-type, Basket-type, and Duplex strainers.

Applications:

Installed at pipeline inlets or upstream of sensitive equipment to trap large debris and prevent mechanical wear.

15/11/2025

WATER TREATMENT PLANT (WTP)

DESIGN

1. Intake Structure

Collects raw water from river/lake and directs it to treatment plant.

2. Screening

Screens remove floating materials like leaves, plastic, debris.

3. Aeration

Aeration allows oxygen to mix with water to remove dissolved gases and reduce odor.

4. Coagulation

Chemical (Alum/Ferric Chloride) is added to water for particle destabilization.

5. Flocculation

Slow mixing allows small particles to combine into larger flocs.

6. Sedimentation

Water is kept in settling tanks where flocs settle at the bottom.

7. Filtration

Water passes through layers of sand & gravel to remove remaining fine particles.

8. Disinfection

Chlorine/UV/Ozone is applied to kill pathogens.

9. Storage & Distribution

Treated water stored in reservoirs and supplied to consumers.

14/11/2025

𝐃𝐢𝐟𝐟𝐞𝐫𝐞𝐧𝐭𝐢𝐚𝐥 𝐏𝐫𝐞𝐬𝐬𝐮𝐫𝐞 Transmitter

In instrumentation, DP (Differential Pressure) isn’t just about pressure difference, it’s one of the most versatile principles in process control.

It measures the difference between two points in a system, and from that single variable, multiple process parameters can be derived.

Here’s how it shows up across plants:

𝐅𝐥𝐨𝐰 𝐌𝐞𝐚𝐬𝐮𝐫𝐞𝐦𝐞𝐧𝐭: Using or***ce plates, venturi tubes, or pitot elements, DP transmitters convert pressure difference into flow rate.

𝐋𝐞𝐯𝐞𝐥 𝐌𝐞𝐚𝐬𝐮𝐫𝐞𝐦𝐞𝐧𝐭: In pressurized or closed tanks, DP transmitters measure the hydrostatic head to determine liquid level.

𝐅𝐢𝐥𝐭𝐞𝐫 𝐌𝐨𝐧𝐢𝐭𝐨𝐫𝐢𝐧𝐠: A rising DP across filters signals clogging or fouling.

𝐏𝐮𝐦𝐩 𝐏𝐞𝐫𝐟𝐨𝐫𝐦𝐚𝐧𝐜𝐞: DP helps track suction vs. discharge pressure to monitor efficiency.

𝐕𝐚𝐥𝐯𝐞 𝐏𝐨𝐬𝐢𝐭𝐢𝐨𝐧 𝐅𝐞𝐞𝐝𝐛𝐚𝐜𝐤: Used to infer actuator movement and detect blockages or restrictions.

Its strength lies in reliability; no moving parts, simple principle, and broad applicability across liquids, gases, and steam.

When properly installed and calibrated, a DP transmitter can serve as the backbone of process insight, quiet, accurate, and dependable.

14/11/2025

a domestic Electrolux (ammonia absorption) refrigeration system in a block diagram form. A gas burner provides heat to the generator, which contains an ammonia-water (NH₃–H₂O) solution. As the mixture boils, ammonia v***r separates and moves through a rectifier to remove excess water. The pure ammonia v***r then condenses in the condenser, turning into liquid ammonia. In the ev***rator, liquid ammonia mixes with hydrogen gas (H₂), lowering its partial pressure and causing it to ev***rate, thus absorbing heat and creating a cooling effect. Meanwhile, the weak ammonia-water solution flows to the absorber, where it reabsorbs ammonia v***r, forming a strong solution again. A heat exchanger improves efficiency by transferring heat between the hot strong solution and the cold weak solution, completing the cycle.

14/11/2025

This diagram represents the components and flow of an air-cooled chiller system, which is designed for efficient cooling. The system consists of several interconnected parts, starting with the compressor (1) and oil separator (2), which help in compressing and separating oils from the refrigerant. The high-pressure gauge (3) and condenser (4) regulate the pressure and heat exchange process, while the expansion valve controls refrigerant flow. The system also includes a circulation pump (16) and an ev***rator tank (12) to manage heat absorption and transfer. Other components, such as the solenoid valve (6), filter dryer (7), and heater (15), ensure proper refrigerant flow, filtration, and temperature regulation. The city water supply (11) and the by-pass valve (18) allow for flexible operation, while the low-pressure gauge (10) monitors system pressure. The diagram illustrates the flow and interaction of the cooling process, highlighting the complexity of an air-cooled chiller's function in temperature management systems.

13/11/2025

A liquid-v***r mixture in a compressor has no significant advantages; in fact, it is detrimental and leads to severe damage, including catastrophic failure. This is because compressors are designed to compress only v***r, and the presence of liquid can cause major problems like mechanical damage to components, reduced efficiency, and increased wear and tear.

Disadvantages of a liquid-v***r mixture in a compressor

Mechanical damage: Liquids are incompressible, and their presence can cause catastrophic failure. In reciprocating compressors, liquid ingestion is particularly problematic and can lead to broken valves, connecting rods, or even the entire compressor.

Increased wear: The liquid can wash away lubricating oil from moving parts, increasing friction, wear, and tear on components like bearings and pistons.

Reduced efficiency: Liquid in the compression chamber can prevent proper sealing and reduce the compressor's volumetric efficiency. This means it can't move the required amount of refrigerant, leading to a decrease in the overall system's performance.

Potential for cavitation and flash gas: Liquid can boil and turn into gas during the compression process, causing pressure fluctuations and potential damage due to cavitation. This is a severe issue in centrifugal compressors.

Increased discharge temperature: Liquid entering the compressor can flash into gas, which can cause a sudden increase in pressure and temperature, leading to a higher discharge temperature and potentially damaging downstream components.

How to prevent a liquid-v***r mixture

Use a separator: An accumulator or separator can be installed before the compressor to remove liquid refrigerant from the flow and ensure only v***r enters the compressor.

Implement a thermostatic expansion valve: An expansion valve is a device that regulates the flow of liquid refrigerant into the ev***rator. Using a thermostatic expansion valve ensures that only v***r enters the ev***rator, preventing liquid from returning to the compressor.

Use an accumulator: An accumulator can be used to store any liquid refrigerant that may be present and prevent it from entering the compressor.

Add heat exchangers: Adding heat exchangers can help ensure that the refrigerant is completely v***rized before entering the compressor.

Envision Engineering & Skill Development

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