Cross-flow LMTD correction factors increase with shell pass count; for a single-pass cross-flow exchanger, the value is__________________?
Show answer Hide answer
Answer: D. < 1
Explanation
Cross-flow LMTD correction factors account for thermal effectiveness deviations caused by fluid flow maldistribution. For a single-pass cross-flow heat exchanger configuration, the flow pattern departs from ideal counter-current behavior. Consequently, the logarithmic mean temperature difference correction factor for this arrangement is always less than one. Correction factors are multiplied by uncorrected LMTD values to determine the true mean temperature difference. Cross-flow arrangements are common in finned-tube air coolers and compact heat exchanger designs. Multipass shells and complex cross-flow layouts have correction factors that depend on temperature ratio parameters.
HVAC coil designers use cross-flow LMTD correction factors to accurately size air-to-refrigerant heat exchangers. Applying uncorrected LMTD values to cross-flow equipment would lead to severely oversized surface area calculations. Understanding correction factors ensures efficient thermal design in industrial gas cooling and waste heat recovery units. A correction factor of zero would imply zero temperature driving force, rendering heat transfer completely impossible. A correction factor of one represents ideal true counter-flow behavior, which single-pass cross-flow exchangers do not achieve. Correction factors for heat exchangers can never exceed one because cross-flow is less efficient than pure counter-flow.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. What is the nutrient composition implied by a -10-5 fertilizer rating______________?
Show answer Hide answer
Answer: A. 5, 10, 5% respectively of N2, P2O5 and K2O
Fertilizer grades conventionally indicate the percentage composition of nitrogen, phosphate, and potash respectively. A standard numeric rating provides guaranteed analysis percentages for these three primary plant nutri...
Q2. How does the required number of stages respond when the reflux ratio in a continuous counter-current extraction setup is elevated_______________________?
Show answer Hide answer
Answer: B. Decrease
Increasing the reflux ratio returns more solvent back into the extraction column. This higher internal liquid traffic enriches the counter-current streams and improves separation efficiency. Consequently, fewer equilibri...
Q3. What is the reaction order depicted in the accompanying graphic, characterized by the rate expression -rA = KCA_________________?
Show answer Hide answer
Answer: D. 3
The rate expression convention and matching graphic coefficients determine reaction kinetics order. Complex chemical kinetics models evaluate the overall exponent sum in rate laws. Based on the provided rate expression p...
Q4. As ambient temperature climbs, the atomic heat capacities corresponding to all solid elemental substances_________________?
Show answer Hide answer
Answer: A. Increases
According to the Dulong-Petit law and general thermodynamic behavior, atomic heat capacities increase at high temperatures. Thermal agitation allows lattice atoms to vibrate with greater amplitudes, absorbing more therma...
Q5. How does the internal energy of a substance respond to an increase in temperature___________________?
Show answer Hide answer
Answer: A. Increases
Internal energy represents the total microscopic kinetic and potential energy stored within a given substance. Raising the temperature increases the average translational and rotational kinetic energy of its constituent...
Q6. What is the amount of work performed during the free expansion of a gas____________________?
Show answer Hide answer
Answer: B. Zero
Free expansion involves a gas rushing into an evacuated chamber against zero opposing external pressure. Mechanical work done is defined as the product of external pressure and the resulting volume change. Since external...